TUNCELI, Turkey (Reuters) -- Turkish troops killed seven Kurdish rebels in an operation in the east of the country on Thursday, a military source told Reuters.

Clashes between Turkish security forces and the banned Kurdistan Workers Party (PKK) have increased since the rebels called off a five-year unilateral ceasefire in 2004.

The military source said the army airlifted more than 500 troops overnight onto the Munzur Mountains on the borders of the eastern Tunceli and Erzincan provinces, after discovering a group of 20 to 30 PKK rebels.

"Clashes are continuing and the operation is ongoing," the source said. He said seven rebels had been killed so far.

Tension has been rising among Turkey's restive Kurds this week with demonstrations across the mainly Kurdish southeast in support of Abdullah Ocalan, the PKK leader jailed for life as the sole inmate in an island prison in the Sea of Marmara.

Turkish leaders have accused Kurdish parties of trying to incite violence and bring the issue of Kurdish rights onto the agenda as the European Union prepares to start accession talks with Turkey on Oct. 3.

More than 30,000 people, most of them Kurds, have been killed since the PKK began its campaign for a separate homeland in 1984.