The attack, the latest in two months of escalating clashes which have brought a peace process to the brink of collapse, did not disrupt the operations of the plant.
Military attack helicopters were searching for the militants from the Kurdistan Workers' Party (PKK) after they fled, the sources said, Reuters reported on Sunday.
Turkey has launched more than 400 air strikes against PKK camps in northern Iraq and southeastern Turkey since late July, in what it says is a response to mounting attacks on police officers and soldiers. Ankara, the United States and European Union all consider the PKK a terrorist organization.
Kurdish activists accuse Turkey of launching the military campaign in a bid to stifle Kurdish political gains in Turkey and territorial ambitions in northern Syria, where groups allied to the PKK have been battling the Islamic State in Iraq and the Levant (ISIL) terrorists. Ankara denies these accusations.
The Turkish army said in a statement that 11 customs officials at a border gate with Iran had been kidnapped by PKK militants on Friday. The PKK has kidnapped state officials in the past, most of whom have later been released.
The unrest comes at a difficult time for the NATO member, which faces a snap election in November after the ruling AK Party lost its majority in a June parliamentary poll for the first time since coming to power more than a decade ago.
It has also left in tatters a ceasefire agreed two years ago with the PKK as part of efforts to end a conflict in the predominantly Kurdish southeast which has killed about 40,000 people over the past three decades.