One Turkish soldier also died in northern Iraq on Friday in clashes with fighters from the Kurdistan Workers' Party (PKK), Turkey's defence ministry said.

Despite official protests from Baghdad, Turkey on Wednesday launched operation "Claw-Tiger" by land and air into the mountainous terrain of northern Iraq where the PKK has bases.

Three civilians were killed Friday when a Turkish air strike hit their cars, said Ouarchine Mayi, mayor of Chiladzi in Dohuk province, which neighbours Syria and Turkey.

Another local mayor, Serbast Sabri, said the body of a fourth civilian was also found, two days after he had gone missing.

A shepherd was killed early Thursday morning when Turkish air raids hit the Bradost district, an official from northern Iraq's autonomous Kurdish region, Ihsan Chalabi, told AFP.

Turkish special forces have landed by helicopter in Iraqi Kurdistan to flush out PKK guerrillas from hideouts in the region's remote mountains.

Turkey has sporadically bombed PKK bases in the region, but its dramatic escalation has prompted scores of families in the area to flee, according to local activists.

The PKK, which Ankara brands a "terrorist" organisation because of its decades-long insurgency against the Turkish state, has not reported any casualties so far.

Iraq's foreign ministry has summoned Turkish ambassador Fatih Yildiz twice this week, demanding Ankara withdraw its special forces and halt the bombing campaign.

But Yildiz has been defiant, telling Iraqi authorities that if Baghdad did not take action against the rebels, Ankara would continue to "fight the PKK wherever it is".

Iraq even summoned Iran's envoy in response to cross-border shelling of Kurdish areas of northern Iraq. Iran, which has its own Kurdish minority, has also been fighting Kurdish rebels who use Iraq as a base.

Saudi Arabia has also condemned the Turkish operations inside northern Iraq.

But there has been no direct comment from Iraqi Foreign Minister Fuad Hussein, who is himself a Kurd and is close to top officials in the autonomous Kurdish region.

The Iraqi Kurdish regional government considers the PKK a rival group but has been unable to uproot it from its mountain hideouts.

It has, however, tolerated the presence of around 10 Turkish military bases inside its territory for the past 25 years.