MOSCOW (AP) -- The latest developments on ongoing Syria peace talks and the pullout of Russian forces from the country (all times local):


8:30 p.m.


Secretary of State John Kerry says he will travel to Moscow next week to discuss Russia's withdrawal of forces from Syria and the political transition process in the war-torn country.


Kerry said Tuesday he would meet Russian President Vladimir Putin with an eye toward pushing peace talks forward in light of the new development, saying "we have reached a very important phase in this process."


Earlier Tuesday, warplanes and troops stationed at Russia's air base in Syria started leaving for home after a partial pullout order from Putin the previous day, a step that raised hopes for progress at newly reconvened U.N.-brokered peace talks in Geneva.


Putin's announcement took the U.S. and many of its allies by surprise. U.S. officials have said they are cautiously optimistic about what the withdrawal may mean.


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8 p.m.


U.N. envoy for Syria Staffan de Mistura has rounded out his team of top advisers with a Russian expert on the Middle East.


U.N. spokesman Ahmad Fawzi said Tuesday that Vitaly Naumkin became a senior adviser to de Mistura a day earlier. A fluent Arabic speaker, Naumkin heads the Moscow-based Institute of Oriental Studies and chaired several rounds of Syrian talks in Moscow last year.


Naumkin joins three other top advisers: Germany's Volker Perthes, who heads a task force on monitoring a two-week old cease-fire in Syria; Jan Egeland, who is leading a task force on humanitarian aid, and Swiss legal expert Nicolas Michel.


De Mistura on Monday restarted indirect peace talks in Geneva between the Syrian government and the opposition.


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7:50 p.m.


The U.N. special envoy for Syria has started a meeting with the opposition after holding a moment of silence to mark the five-year anniversary of the uprising against President Bashar Assad.


Staffan de Mistura asked for a minute of silence as he convened envoys from the High Negotiations Committee on Tuesday. Several attendees folded their arms, and some appeared to pray.


De Mistura restarted indirect Syrian peace talks in Geneva a day earlier by meeting with envoys from Assad's government.


Many observers say the peace talks offer the best chance in years to end Syria's conflict, which has left at least 250,000 people dead and displaced millions.


The uprising began with mostly peaceful protests. A brutal government crackdown fueled the rise of an armed insurgency, plunging the country into a full-blown civil war that has sucked in regional and global powers.


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7 p.m.


U.N. Secretary-General Ban Ki-moon is appealing to all parties in the Syria conflict to make the current negotiations successful, warning that the consequences of failure "are too frightening to contemplate."


Marking the fifth anniversary of the Syrian uprising on Tuesday, Ban said President Bashar Assad's government could have responded to the demands of protesters "with genuine dialogue and reform."


He said other states in the region and elsewhere could have united to help stabilize Syria rather than use it as a battlefield.


Instead, Ban said, over 250,000 people have been killed, nearly half the population has been forced from their homes, and the world has been confronted "with an unprecedented humanitarian catastrophe."


Ban said those responsible for using chemical weapons, siege and starvation as a tool of war, torture and indiscriminate bombing of civilians "must be held to account." He again urged the U.N. Security Council to refer the situation in Syria to the International Criminal Court.


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6:20 p.m.


A Syrian opposition monitoring group is reporting intense airstrikes in and around the historic town of Palmyra amid fighting between pro-government forces and the Islamic State group.


The Britain-based Syrian Observatory for Human Rights says there were casualties on both sides in Tuesday's battles, without providing a precise figure.


Al-Manar TV, run by Lebanon's militant Hezbollah group, says Syrian troops and their allies captured "Hill 900," which is the highest in the area and overlooks Palmyra.


Hezbollah is fighting alongside forces loyal to Syrian President Bashar Assad.


Palmyra, home to famed Roman ruins, has been under the firm control of IS since the extremists captured it in May last year.


IS and al-Qaida's branch in Syria, known as the Nusra Front, are not part of a cease-fire that was brokered by Russia and the U.S. and went into effect on Feb. 27.


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6:15 p.m.


A senior U.N. official says Russia's decision to withdraw military forces from Syria is an "encouraging sign" that the international community is united behind peace efforts.


U.N. Under-Secretary-General for Political Affairs Jeffrey Feltman said Tuesday that a recent cease-fire has allowed for greater deliveries of humanitarian aid and "significantly" reduced violence.


President Vladimir Putin on Monday announced the planned withdrawal of most Russian forces from Syria, hours after indirect peace talks between Syrian President Bashar Assad's government and the opposition began in Geneva.


Russia launched an air campaign last year in support of Assad's forces that allowed them to make significant advances across the country.


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6 p.m.


The head of a U.N. commission investigating human rights abuses in Syria says Russia's decision to begin withdrawing forces shows a commitment by President Vladimir Putin to support peace talks.


Paulo Pinheiro declined to characterize the impact of Russia's air campaign in support of Syrian President Bashar Assad's forces, which began in September. He told reporters Tuesday that his commission of inquiry does not "distribute grades for the performance of states."


The head of the U.N. Commission of Inquiry on Syria said "it would be fair to recognize" that Putin's surprise announcement a day earlier of the Russian drawdown showed "a very clear commitment" to the need to support U.N.-mediated indirect peace talks in Geneva between the Syrian government and the opposition.


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4:40 p.m.


Britain's foreign minister says he is skeptical about Russia's announced military withdrawal from Syria.


Foreign Secretary Philip Hammond told lawmakers in the House of Commons that Russia had made past pledges to pull its troops out of Ukraine, "which later turned out to be merely routine rotation of forces."


He says that "because Russia is completely un-transparent about its motives and its plans, we can only speculate."


Hammond says a genuine de-escalation by Russia "would be welcome," and urges Moscow to use its influence on President Bashar Assad's government to seriously engage with the opposition.


Hammond said that "Russia has unique influence to help make these negotiations succeed and we sincerely hope that they will use it."


2:50 p.m.


The head of Russia's Air Force says that in more than five months of Russian airstrikes in Syria, not a single bomb missed its target.


Col.-Gen. Viktor Bondarev made the claim on Tuesday in ceremony near Voronezh, welcoming the first contingent of warplanes to return from Syria a day after the surprise announcement of a Russian pullback. Voronezh is 500 kilometers or 300 miles south of Moscow.


During Russia's airstrikes, which Moscow said were aimed against extremist groups such as the Islamic State and the Nusra Front, there were claims from Syrian groups that Russian bombs had hit civilians and that many of the attacks were aimed not against extremists but at more moderate forces fighting Syrian government troops.


But Bondarev said that "there was not one bombing that was not on target, not one bombing of sensitive objects," according to Russian news agencies.


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2:30 p.m.


An adviser to Iran's supreme leader has told visiting Syrian deputy foreign minister that Iran hopes Syria peace talks in Geneva will be a success and that the Damascus government will be "victorious against enemies."


The official IRNA news agency cited Ali Akbar Velayati as telling Syrian Deputy Foreign Minister Faisal Mekdad on Tuesday that Tehran officials "are hopeful that you succeed in the talks as you were successful in war and defending Syrian territory."


Velayati, an adviser to Ayatollah Ali Khamenei, says that "despite plenty of damages to Syria, the country resisted against serious attacks, equivalent to a little world war, and became victorious."


He says that Iran, as well as Shiite-led Iraqi Cabinet and the Lebanese Hezbollah group, played a key role in helping Damascus' government.


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1:40 p.m.


A Russian deputy defense minister says Russian warplanes based in Syria will continue striking militants from the Islamic State group and Syria's al-Qaida branch, known as the Nusra Front, as well as other militant factions which the U.N. Security Council has designated as terrorist organizations.


Deputy Defense Minister Nikolai Pankov took part in a ceremony at Russia's air base in Syria on Tuesday honoring the departing Russian pilots.


He says that while the Russian air campaign had brought positive results, it was too early to speak about victory over terrorism and the Russian forces remaining in Syria "have the task of continuing to strike terrorist targets."


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1:30 p.m.


Iranian Foreign Minister Mohammad Javad Zarif is welcoming Russia's decision to begin withdrawing forces from Syria, where a fragile cease-fire is holding.


"The fact that Russia announced that it's withdrawing part of its forces indicates that they don't see an imminent need to resort to force in maintaining the cease-fire," Zarif said during a speech at the Australian National University, in Canberra. "That in and of itself should be a positive sign. Now we have to wait and see."


Zarif is first Iranian foreign minister to visit Australia since 2002.


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11:05 a.m.


The U.N. special envoy for Syria is calling Russian President Vladimir Putin's announcement of the partial pullout of Russian troops from the Mideast country a "significant development."


According to a statement Tuesday in Geneva, Staffan de Mistura said his team hopes the Russian drawdown will have a "positive impact" on the negotiations aimed at finding a political solution to Syria's war and "a peaceful political transition in the country."


De Mistura reconvened indirect peace talks between Syrian government representatives and those of the so-called moderate opposition a day earlier, just hours before Putin's announcement.


After meeting with a government delegation on Monday, he was to meet with opposition representatives on Tuesday.


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10:50 a.m.


The head of the defense committee in Russia's upper house of parliament has estimated that about 1,000 Russian military personnel will remain in Syria at Russia's two bases.


The head of the parliamentary defense committee, Viktor Ozerov, said Tuesday that he estimated about 1,000 Russian military personnel would remain in Syria at the two bases. That's according to the Interfax news agency.


Ozerov says Russia would need a minimum of two battalions, a total of 800 troops, to protect the two bases. He says it will continue to conduct air reconnaissance, requiring some of the plane crews to remain, and the military specialists advising the Syrian army also would stay.


The estimate follows President Vladimir Putin's announcement Monday that some of the Russian aircraft and troops would be withdrawn. Russia has not revealed how many soldiers it has deployed to Syria, where it maintains a naval facility as well as an air base, but U.S. estimates of the number of Russian military personnel varies from 3,000 to 6,000.


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10:30 a.m.


Russia's defense ministry says the first group of warplanes has left the Russian air base in Syria.


Tuesday's departure follows Russian President Vladimir Putin's announcement the previous night that Russia would be withdrawing most of its forces from Syria, including some of the aircraft.


The defense ministry says the first group has left Syria, including an unspecified number of Su-34 warplanes.


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9:15 am.


Russia's defense ministry says its military at the Russian air base in Syria is preparing for some of the planes and fighter jets to leave and return home.


Tuesday's statement comes a day after President Vladimir Putin ordered the Russian military to withdraw most of its forces from Syria, timing his move to coincide with the resumption of Syria peace talks in Geneva.


The ministry says Russian personnel are currently loading equipment and materiel on cargo planes and getting ready for the withdrawal, which marks an end to Russia's five-and-a-half-month air campaign.


Russian air strikes have allowed Syrian President Bashar Assad's army to win back some key ground and strengthen his positions ahead of the Geneva talks.


The ministry did not indicate when the first planes are scheduled to leave.


By AP