Turkish forces stage raid into Iraq

· 10,000 troops said to be pursuing Kurdish rebels
· Ankara says it gave US warning of incursion

Thousands of Turkish troops, supported by aircraft and artillery, crossed into northern Iraq on Thursday in what appeared to be an escalation of their campaign to hunt down rebels of the Kurdistan Workers Party (PKK), believed to be sheltering in the remote mountain areas straddling the Turkish-Iraqi border.

The Turkish military said the ground operation started after warplanes and artillery attacked a number of targets inside Iraqi territory. Turkish television said up to 10,000 troops, backed by planes and helicopters, moved 16 miles beyond the border. Ankara said it had given Iraqi and US leaders advance warning.

A PKK spokesman said last night its fighters had killed 22 Turkish soldiers and wounded many more during clashes that continued yesterday. Neither the casualties nor the location of the fighting could be verified.

Senior Iraqi Kurdish officials last night played down the reports of a large-scale incursion, saying Turkish forces had entered the largely uninhabited area of Rykan, a few miles into Iraqi territory, and had since mostly returned across the border. "It was a show of force, designed to meet Turkish public opinion at home, and test the reaction of Baghdad and Washington. They were far from our forces," one official said.

The main border crossing between Turkey and Iraq was operating normally last night.

News of the operation brought calls for restraint from Britain, Europe and the US. Washington has effectively given the Turks a green light for limited military operations in the north and has been providing Turkey with satellite and other intelligence on PKK movements.

In Baghdad Rear Admiral Gregory Smith, a US military spokesman, said the military had received assurances from Turkey, a Nato ally, that the operation would be of "limited duration" and everything possible would be done to avoid "collateral damage to innocent civilians or Kurdish infrastructure".

But US state department officials were less sanguine. It was "not the greatest news", said the deputy assistant secretary of state Matthew Bryza. "A land operation is a whole new level."

There are fears that expanded Turkish military activities in the north could exacerbate tensions with Iraq's Kurds, undermining the only secure area in the country and damaging Iraq's territorial integrity. Britain urged Turkey to leave Iraqi territory as soon as possible.

Iraqi Kurdish officials were far more concerned about another incident on Thursday, when 12 Turkish tanks were confronted by Kurdish security forces as they tried to leave their base in a disused airport at Barmani, about 40 miles inside Iraq. Under an agreement with Kurdish leaders hammered out in the 1990s, the Turks have kept a few thousand troops in the north to "monitor" PKK movements.

Kurdish officials said the Turkish tanks had attempted to leave their base without first notifying local security forces. "It went against the conditions of the agreement and they were requested by our peshmerga to return to their base," said an aide to Kurdistan's regional president, Massoud Barzani.