Jens Stoltenberg, NATO secretary-general, has called an emergency meeting on Tuesday to discuss security at the request of Turkey after last week's suicide bombing there and ongoing Turkish security operations on two fronts.

NATO said in a statement on Sunday that the North Atlantic Council, which includes the ambassadors of all 28 NATO allies, would meet following a request by Turkey to hold consultations under Article 4 of NATO's founding Washington Treaty.

Turkey announced on Friday a double military offensive, one against the Islamic State of Iraq and the Levant (ISIL) group across the border in Syria, and the other targeting Kurdish PKK fighters in northern Iraq.

"Turkey requested the meeting in view of the seriousness of the situation after the heinous terrorist attacks in recent days, and also to inform allies of the measures it is taking," NATO said.

"NATO allies follow developments very closely and stand in solidarity with Turkey."

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In Article 4, members are encouraged to bring subjects to the table for discussion for political consultation.

Since the alliance's creation in 1949, Article 4 of NATO has been invoked several times, such as by Turkey in 2003 and in 2012, and Poland in 2014.

Patriot batteries

Germany, the Netherlands, and the US each sent two Patriot anti-missile batteries and soldiers to operate them at the start of 2013 after Turkey asked for NATO help in increasing border security due to the civil war in Syria.

Turkish F-16 fighter jets hit PKK targets in northern Iraq late on Sunday, Turkish security sources said.

The jets, which hit targets in Hakurk, scrambled from the airbase in Diyarbakir, the sources said.

Earlier, Turkey's army blamed the "separatist terror organisation" for a car bomb in Diyarbakir that killed two soldiers late on Saturday. Turkey never refers to the PKK by name.

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

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

The tensions in Turkey follow a suicide bombing in the southern town of Suruc earlier in the week that killed dozens of Kurdish activists.

Turkish authorities blamed ISIL for that attack.

Ahmet Davutoglu, Turkish prime minister, has said the military operations would not have a timeframe, indicating a prolonged offensive.

Ceasefire at risk

For its part, the PKK said the Turkish air strikes on its bases meant the government in Ankara had ended a fragile 2013 ceasefire between the two sides.

The PKK has for decades waged an armed campaign in Turkey's southeast that has claimed tens of thousands of lives.

A peace process that began in 2013 has so far failed to yield a final deal.

Against this backdrop, Turkish police and protesters on Sunday engaged in clashes in the Istanbul district of Gazi, where a leftist activist was killed during police raids earlier this week.

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

A police officer 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.

Some in the Turkish opposition say they are concerned the governing AK party's aims with new attacks on the PKK to stir up anti-Kurdish sentiment before a possible early election later this year.