The soldiers died in separate incidents in the provinces of Hakkari and Sirnak, both bordering Iraq, when home-made bombs planted by Kurdish rebels exploded, the army said on its web site.

Clashes in the same region claimed seven lives Friday, prompting also cross-border air raids on targets in northern Iraq, where the rebels have rare bases.

The operation against the outlawed Kurdistan Workers' Party (PKK) began after a group of about 25 militants attacked a commando unit near the border village of Daglica Friday morning, killing two soldiers.

At least five PKK militants were killed in the ensuing clashes.

"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, the army said late Friday.

"It has been observed that those positions were destroyed.

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

Winter lulls in the 25-year conflict are usually broken with the arrival of spring when the snow melts, allowing the rebels to move out from their mountainous hideouts in Turkey and Iraq.

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 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. The mandate 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.