At least four police officers have been killed in a bomb attack in Turkey's southeastern province of Mardin, reports say.

The officers were traveling on Thursday in a vehicle in the province when explosives believed to have been planted by Kurdish militants were detonated as they passed by, security sources told Reuters.

The blast is seen as the latest in an upsurge of almost daily attacks against security forces by Kurdistan Workers' Party (PKK) militants since the collapse of a two-year ceasefire in July.

In an earlier attack, PKK militants sprayed a police car with bullets in Batman Province, also in the southeast, on Tuesday, triggering an exchange of gunfire.

A militant was killed during the gun battle while a policeman sustained grave gunshot injuries. The officer later succumbed to his wounds in a nearby hospital.

Separately, two army troops were injured when PKK militants launched an attack on a military base in the Uludere district in Turkey’s southeastern province of Sirnak on Tuesday.

The developments came a day after at least five Turkish police officers sustained injuries when a bomb explosion ripped through their patrol vehicle in Sirnak Province on the highway linking the districts of Idil and Cizre in the province on Monday.

[caption id="" align="alignnone" width="555"] A missile-loaded Turkish Air Force warplane takes off from the Incirlik Air Base, in the outskirts of the city of Adana, southeastern Turkey, on July 28, 2015 to strike ‘militant targets in Syria.’ (AFP photo)[/caption]

This is while, Turkey has been launching airstrikes against PKK positions in Iraq.

The PKK has been fighting for an autonomous Kurdish region inside Turkey since the 1980s. The conflict has left tens of thousands of people dead.

By Press TV