The army said it used artillery and airstrikes against a group of "50 to 60 terrorists ... inside Iraq's borders" southeast of the Turkish town of Cukurca in Hakkari province in the mountainous Turkey-Iraq border region.

"If necessary, other army units will intervene in the region," it added.

A senior PKK leader denied the strikes had occurred.

"There are no clashes with the Turkish army. Our area is quiet ... There are no airstrikes nor any artillery shells," he said by telephone from a rebel base near the Iraq-Turkey border.

"There has been no crossing of Turkish troops into the Kurdistan region," added the official, who asked not to be named.

Contacted in the Iraqi Kurdish city of Arbil, Fuad Hussein, chief of staff for Massud Barzani, the president of Iraq's Kurdish region, did not categorically confirm the strikes but said "it could be artillery shelling."

He said a ground assault by Turkish forces was not expected given the "prevailing weather conditions."

Jabbar Yawar, the head of peshmerga forces in northern Iraq, said without elaborating that Turkish aircraft had been "trespassing northern Iraqi airspace for a week."

The US military in Baghdad said it had no reports of Turkish military operations in northern Iraq.

"We have nothing. We have no reports like that at all," spokesman Major Winfield Danielson told AFP.

Asked if the US military would know if Turkish troops had crossed the border, he replied, "I can't answer that. I don't know if we would."

Turkish troops also intensified operations against Kurdish rebels inside Turkey near the Iraqi border, Anatolia news agency reported.

Combat helicopters hit various locations in a bid to prevent rebels from returning to their bases in Iraq, the agency said.

Tensions along the Turkish-Iraqi border increased after October 21, when PKK militants ambushed a military unit, killing 12 soldiers and capturing eight. The captives were released in November.

Soon after, the Turkish government secured parliamentary approval for cross-border military operations into northern Iraq.

In recent weeks Turkey deployed around 100,000 soldiers along its 380-kilometre (240-mile) border with Iraq in the mainly Kurdish south-east region of Anatolia.

Saturday's operation came days after the cabinet of Prime Minister Recep Tayyip Erdogan authorised the army to carry out a cross-border operation -- a month after the green light from parliament.

The Turkish parliament's decision last month provoked a flurry of diplomatic activity between Turkey, Iraq and the United States.

Both the United States and Iraq were keen to avert a large scale incursion in the region, a relatively peaceful area of the war-torn country.

Baghdad promised to rein in the Kurdish rebels in the north of the country, and in early November President George W. Bush said the United State would provide "real-time" information on PKK movements from its satellites.

The pledge was largely seen as tacit US approval for limited cross-border Turkish strikes, notably air raids, against PKK targets.

Ankara made it clear that it would be keeping its options open and refused to rule out a military response to any PKK activity.

The PKK, listed as a terrorist group by Ankara and much of the international community, has waged a 23-year armed campaign for Kurdish self-rule in Turkey's southeast. The conflict has claimed more than 37,000 lives.

Kurdish speakers are also present in Iran and Syria. The PKK is thought to number around 5,000 rebels including some 3,500 in the Iraqi mountains.

Armagan Kuloglu, a former general turned military analyst, said that Saturday's operation was not the prelude to a large scale incursion although similar actions including special forces missions may follow.

"It is an operation against a very precise target and this is not a surprise given that Turkey has said and repeated that it was going to crack down on terrorists in northern Iraq," Kuloglu told television channel NTV.

Turkey, where the army continues to wield strong influence in national politics, has the second largest army in NATO after the United States with around 515,000 troops.