BAGHDAD - Iraq on Tuesday condemned Turkey's incursion into northern Iraq to fight Kurdish guerrillas in the strongest terms so far and demanded an immediate end to what it called a violation of its sovereignty.

Thousands of Turkish troops crossed the border last Thursday to root out PKK fighters who have used mountainous northern Iraq as a base for their fight for self-rule in the mainly Kurdish southeast of Turkey since the 1990s.

"The cabinet expressed its rejection and condemnation for the Turkish military interference, which is considered a violation of Iraq's sovereignty," the Iraqi government said in a statement released by spokesman Ali al-Dabbagh.

"The cabinet stresses that unilateral military action is not acceptable and threatens good relations between the two neighbours."

Dabbagh said earlier on Tuesday that a Turkish envoy would meet Iraqi President Jalal Talabani, a Kurd, and government leaders including Foreign Minister Hoshiyar Zebari in Baghdad on Wednesday.

An Iraqi government source identified the envoy as Ahmet Davutoglu, a senior foreign policy adviser to Turkish Prime Minister Tayyip Erdogan. Ankara has not confirmed this.

Turkish troops, backed by warplanes, attack helicopters and artillery, have been fighting Kurdish guerrillas at close quarters as they advance on Kurdistan Workers Party (PKK) bases.

"Turkey is engaged in a legitimate fight against a terrorist organisation which has challenged Turkey's peace and security," Erdogan told his AK Party in parliament.

"Turkey has the right to defend its unity and to fight people who try to harm that unity," he said, adding that Turkey respects Iraq's territorial integrity.

The Turkish General Staff said on Tuesday two more of its soldiers had been killed, taking the total to 19. It says at least 153 PKK fighters have been killed. PKK statements that 81 Turkish troops have been killed could not be verified.

The General Staff said heavy snow was hampering the advance of its troops towards PKK camps in the remote, mountainous area.

FIGHTERS KILLED

A senior military official in the U.S.-led coalition in Iraq said about 2,000 Turkish troops were operating inside northern Iraq. Turkish officials have put the number at around 10,000.

A Turkish security source said most of the Turkish troops inside Iraq were involved in an attack on a key PKK command centre in the Zap valley after taking control of the PKK's Haftanin camp about 5 km (3 miles) inside the Iraqi border.

Fighting was concentrated on a strategic hill which controls the entrance to the valley, said the source, who added that at least 21 PKK fighters had been killed since late on Monday.

Other Turkish security sources said the military was trying to destroy PKK bases across northern Iraq as far as a stronghold in the Qandil mountains to prevent a spring offensive by the PKK inside Turkey.

They said hundreds of Turkish special forces were leading the fight, aimed at the PKK's leadership, and troops had advanced as far as 30 km (20 miles) inside Iraq.

Dabbagh said Baghdad feared the operation could expand if peshmergas, Kurdistan's security forces, became involved.

"We want to maintain good relations with Turkey," Dabbagh told an earlier news conference.

"Turkey has to understand the serious situation which might develop as a result of a military mistake which might take place between the peshmergas and Turkish forces," he said.

Kurdistan's peshmergas have so far stayed on the sidelines. Iraqi Kurds have little sympathy for the PKK but there is widespread anger at the incursion.

Ankara, under growing pressure at home, launched the operation last week after saying Iraqi authorities had failed for years to crack down on the rebels. Turkish officials have stressed the offensive will be limited.

Baghdad has called for a diplomatic solution to the PKK problem. It says it has taken some measures to deal with the rebels but is focused on trying to stabilise the rest of Iraq.

The area, near rich oil reserves, has been one of the few relatively stable regions since the U.S.-led invasion to topple Saddam Hussein in 2003. Washington has said the incursion should be as kept as short as possible.

Erdogan said on Tuesday that Turkey was receiving intelligence cooperation from the United States.

Turkey blames the PKK, defined as a terrorist group by the United States and the European Union, for the deaths of nearly 40,000 people since it began its armed struggle for self-rule in mainly Kurdish southeast Turkey in 1984.