Iranian naval vessels fired what appeared to be warning shots over a Singapore-flagged ship in international waters in the Gulf on Thursday, prompting it to flee to United Arab Emirates waters, U.S. officials said.

The Alpine Eternity, a 29,130 gross tonnes oil products tanker, has safely reached the UAE port of Jebel Ali after coming under attack in the Gulf, its manager said.

The UAE sent Coast Guard vessels toward the ship once it reached UAE waters and the Iranian Revolutionary Guard Corps Navy ships turned away, one U.S. official told Reuters, adding the account was based on preliminary information.

The officials, who spoke on condition of anonymity, were unaware of any U.S. Navy involvement.

A spokesman for the vessel's Norwegian manager Transpetrol said it was attacked at sea at 0800 GMT on Thursday on its way to the UAE port of Fujairah.

"The nature of the attack is still unclear," the spokesman said. "She reached UAE waters and she is in the port of Jebel Ali now. The vessel is safe and there are no injuries to crew."

The spokesman said the attack had been reported to Singaporean authorities.

A second U.S. official said there were about five Iranian ships and described the shots as �small arms fire.�

"Once the ship went into UAE territorial waters, the Iranian ships broke off," the official said, also speaking on condition of anonymity.

U.S. President Barack Obama and leaders from Gulf nations are set to meet Thursday in a rare, high-profile summit on U.S. efforts to broker a nuclear deal with Iran. The United States and five other world powers are in talks with Tehran to curb its nuclear program.

Iran, currently in a standoff with a Saudi-led coalition over security inspections of one of its own cargo ships, last month intercepted a Marshall Islands-flagged vessel in the Strait of Hormuz. It forced that ship into Iranian waters by firing shots across its bow.

Saudi-led forces have imposed inspections on ships

entering war-torn Yemen in an attempt to prevent weapons being smuggled to the Iran-allied rebel Houthi group that controls much of the country.

Iran complained to the UN Security Council of the Saudi-led coalition's forces hindering its attempts to send aid to Yemen as a standoff loomed on Wednesday over an Iranian cargo ship bound for the Arabian Peninsula.

Gulf Arab nations in the military coalition have since March 26 been bombing Houthi militia and allied army units that control much of Yemen as well as inspecting ships in a bid to stop weapons smuggling.

Iran said on Wednesday it would not allow coalition forces to inspect the humanitarian shipment. Saudi Arabia has accused Tehran of arming the Houthis, charges the Islamic Republic denies.

Millions of barrels of oil pass through the Bab el-Mandeb and Strait of Hormuz every day to Europe, the United States and Asia, waterways which pass along the coasts of Yemen and Iran respectively.

By Reuters