Istanbul (AFP) - The Turkish military on Sunday launched new air strikes on Kurdish militants in northern Iraq as Ankara invoked an article of NATO to call a meeting of the military alliance over its campaign against the PKK separatists and IS jihadists.

Turkey has launched a two-pronged "anti-terror" cross-border offensive against Islamic State (IS) jihadists and Kurdistan Workers Party (PKK) militants after a wave of violence in the country, pounding their positions with air strikes and artillery.

Protests meanwhile raged in a flashpoint district of Istanbul after raids against suspected militants earlier in the week, leaving one policeman dead.

The Turkish army earlier Sunday blamed PKK militants for a deadly car bomb attack that killed two of its soldiers in the Kurdish-dominated southeast, as a fragile truce risked collapsing.

In the latest strikes, Turkish F-16s took off from Diyarbakir in southeastern Turkey and headed towards the PKK's rear bases in Mount Kandil, CNN-Turk and NTV channels said.

"At around 9:00pm (1800 GMT), Turkish planes started bombing some of our positions in two areas" north of Dohuk and north of Arbil, a spokesman for the PKK in Iraq, Bakhtiar Dogan, told AFP.

Ankara started its campaign on Friday against IS targets in Syria but then expanded it to PKK rebels in neighbouring northern Iraq who are themselves bitterly opposed to the jihadists.

The PKK on Saturday said that the conditions were no longer in place to observe the ceasefire after the heaviest air strikes on its positions in northern Iraq since August 2011.

The car bomb went off as the soldiers were travelling on a road in the Lice district of Diyarbakir province late Saturday, killing two soldiers and wounding four, the statement from the local governor's office said.

The army blamed the "Separatist Terror Organisation" for the attack, using its customary phrase for the PKK which it never refers to by name.

The PKK's military wing, the People's Defence Forces (HPG), claimed the attack in a statement on its website but gave much higher toll of eight soldiers killed.

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The HPG said three more PKK fighters had been killed in Turkish air strikes Saturday, after one was killed in the first wave.





- 'Turkey invokes NATO Article 4' -





Prime Minister Ahmet Davutoglu ordered the campaign after a week of violence in Turkey that began on Monday with a suicide bombing blamed on IS in a town close to the Syrian border that killed 32.

This incensed Turkey's Kurds, who have long accused the government of actively colluding with IS, allegations Ankara categorically denies.

Two Turkish policemen were shot dead Wednesday while sleeping in their homes in the southeast, in murders claimed by the PKK.

Meanwhile Turkey, NATO's only majority Muslim member, called a meeting of ambassadors of NATO states on Tuesday for talks on the violence and its military operations, NATO and the Turkish foreign ministry announced.

"NATO Allies follow developments very closely and stand in solidarity with Turkey," NATO said.

Ankara invoked a clause from NATO's founding treaty that allows any member to request a meeting of all 28 NATO ambassadors "whenever, in the opinion of any of them, their territorial integrity, political independence or security is threatened."

The Article 4 of the Washington Treaty invoked by Turkey has been employed only rarely and usually by Ankara -- it was invoked by Turkey also in 2003 over the Iraq war, in 2012 for the Syria war and by Poland in 2014 over the Ukraine crisis.

With Washington gladdened by Turkey's readiness to step up its role in the coalition against IS, the White House backed Turkey's right to bomb the PKK which the United States categorises as a terror group.

German Chancellor Angela Merkel however urged Turkish Prime Minister Ahmet Davutoglu "not to give up the peace process with the Kurds but to continue it despite all the difficulties," her spokesman Georg Streiter said in a statement





- Protests shake Turkey -





Tensions across the country are high, with police routinely using water cannon to disperse nightly protests in Istanbul and other cities denouncing IS and the government's policies on Syria.

Turkish police and protesters on Sunday engaged in new clashes in the flashpoint Istanbul district of Gazi, where a leftist activist was killed during police raids earlier this week, leaving one policeman dead.

Leftist protesters hurled stones and Molotov cocktails at the police who responded with water cannon and plastic bullets, an AFP correspondent said.

Policeman Muhammet Fatih Sivri was shot in the chest from inside a building while he tried to make an arrest during clashes, the official Anatolia news agency said. He was rushed to hospital but died from his wounds.

Turkish security forces have since Friday rounded up at least 851 suspected members of IS, the PKK and the Marxist Revolutionary People's Liberation Party Front (DHKP-C) across the country on the grounds that they pose a threat to the state, Anatolia said.