DIYARBAKIR, Turkey (Reuters) - The driver of a freight train was wounded on Sunday when a bomb left on a railway track in southeastern Turkey was detonated as the train came past, security sources said, blaming Kurdish militants for the explosion.

The train's locomotive was damaged in the incident near the town of Saray in Van province, near the Iranian border, the sources said.

There were no immediate claims of responsibility.

The Kurdistan Workers Party (PKK), which has waged a three-decade insurgency against Turkish forces, has previously attacked railroads, pipelines and other targets it considers as Turkey's strategic assets.

Four PKK militants were killed in clashes elsewhere in the mainly Kurdish region, the security sources said on condition of anonymity.

Soldiers carrying out operations against the PKK in Diyarbakir province killed one militant on Sunday and seized weapons and narcotics, the sources said.

Further east in Hakkari province, Turkish warplanes bombed suspected PKK targets and killed one militant, while soldiers killed two rebels when a firefight broke out.

The two-year ceasefire between the PKK and the Turkish state collapsed in mid-2015, sparking the worst violence in nearly two decades of fighting. Thousands of rebels, soldiers and civilians have been killed.

(Writing by Ayla Jean Yackley; Editing by Alison Williams and David Goodman)