ISTANBUL: The Turkish military said Friday it had killed 12 Kurdish militants in southeast Turkey and another six in air strikes in northern Iraq, while also targeting their allied fighters in northern Syria.

Twelve of the Kurdistan Workers Party (PKK) guerrillas were "neutralized" Thursday in the Cukurca district of Hakkari province, near the Iraqi border, the army statement said.

In northern Iraq, the Turkish air strikes hit the Avashin Basyan region, killing six PKK fighters and destroying four targets Thursday, it added.

In another statement on its operation to drive ISIS and the Kurdish YPG militia away from the border in northern Syria, the army said it fired on 40 ISIS and six YPG targets Thursday, leaving them 'incapable of manoeuvre'.

On Wednesday night, Turkish air strikes pounded YPG fighters and allied fighters in northern Syria and the army said it killed between 160 and 200 combatants.

Syria's military called the strikes by Turkey there an act of "blatant aggression" and said it would bring down any Turkish war planes entering Syrian air space.

The United States has backed the YPG in its fight against ISIS, infuriating Ankara, which sees the YPG as an extension of the PKK, which has waged a three-decade insurgency in southeastern Turkey.

President Tayyip Erdogan warned Wednesday that Turkey could act alone in rooting out its enemies abroad.

More than 40,000 people, most of them Kurds, have been killed in Turkey's conflict with the PKK, which Ankara, the United States and European Union designate a terrorist organisation.