Bombardments began at 11:00 pm (2000 GMT) on Thursday and targeted Kurdistan Workers' Party (PKK) hideouts in the Qandil mountains along the Iraq-Iran border, a statement from the military said.

All planes returned safely to their bases after strikes deemed as "comprehensive and efficient," the statement added.

Turkey's NTV television news reported that 50 fighter jets participated in the raid, while the pro-PKK Firat news agency said the bombing lasted three hours.

Speaking in northern Iraq, PKK spokesman Ahmed Danis said the rebels had suffered no losses in the strikes but expressed concern that the Turks and the Iranians were increasing their cooperation to try and snuff the rebels out.

"There is co-ordination between Iranian and Turkish militaries to attack PKK and Pejak," Danis said, referring to an Iranian offshoot of the Kurdish rebel group.

"We have information suggesting that there was a meeting between Turkish and Iranian sides on Wednesday, April 30. The meeting was near the border but inside Iranian territory and aimed at locating the places they want to attack later."

Turkish warplanes have been bombing PKK positions in northern Iraq since mid-December. In February, the army conducted a week-long ground offensive against rebel hideouts in the region, where Ankara estimates more than 2,000 militants take refuge.

Turkey's parliament authorised cross-border military action against the rebels for a period of one year in October, paving the way for the ground offensive, which was preceded by five bombing raids on PKK targets in northern Iraq.

Washington backed the Turkish incursion by supplying its NATO ally with intelligence on PKK movements.

But wary of tensions in a relatively stable region of conflict-torn Iraq, the United States also pressed Turkey to end the offensive quickly and step up cooperation with Baghdad and Iraqi Kurds to resolve the problem.

The army said the offensive had dealt a serious blow to the rebel group, with at least 240 militants killed and dozens of hideouts, training camps and ammunition depots destroyed.

The PKK claimed to have killed around 100 soldiers, lost five of its own fighters and downed a Turkish attack helicopter during the incursion.

The United States said the incursion was "targeted and relatively short" and reasserted its support for Turkey against the PKK, listed as a terrorist group by Ankara and much of the international community.

Ankara is under pressure from Washington and at home to back up military action against the PKK with political and economic gestures to the sizeable Kurdish community and erode popular support for the rebels.

Kurdish activists have urged the government to issue a general amnesty for the PKK to encourage the militants to lay down arms.

The Turkish military has warned it will carry out more cross-border strikes on the rebels if need be.

The PKK, listed as a terrorist group by Turkey and much of the international community, has been fighting for self-rule in Turkey's mainly Kurdish southeast since 1984. The conflict has claimed more than 37,000 lives.