"After detecting that anti-aircraft fire was opened on (Turkish) helicopters from various positions across the border, the air force fired on those positions" for an hour Friday afternoon, the army said in an online statement.

"It has been observed that those positions were destroyed," it said.

The operation against the separatist Kurdistan Workers' Party (PKK), which has rear bases in Iraq, began after a group of about 25 rebels attacked a commando unit near the border village of Daglica Friday morning, killing two soldiers.

The statement confirmed that at least five PKK militants were killed in the ensuing clashes.

"Operations in the region are continuing and it is believed that the losses of the terrorists are higher," it said.

The Turkish army has staged a series of air raids against PKK bases in northern Iraq since December 2007, often with the help of US intelligence, and in February 2008 carried out a week-long ground incursion.

In October 2007, Daglica, nestled among rugged mountains, was the scene of one of the bloodiest PKK attacks in recent years in which rebels sneaking in from Iraq ambushed a patrol, killing 12 soldiers and wounding 17 others.

The attack turned up pressure on the government for cross-border military action against the PKK, paving the way for subsequent parliamentary authorisation to that effect, which expires in October.

The PKK, listed as a terrorist group by Turkey and much of the international community, took up arms against Ankara in 1984, sparking a conflict that has claimed about 45,000 lives.