"In accordance with our right to self-defence... air operations were carried out against terrorist targets in northern Iraq in the regions of Metina, Hakurk, Gara, Qandil and Asos, and in northern Syria," the Turkish defence ministry said in a statement.

The Turkish army claimed to have hit 24 targets, "including caves, shelters, ammunition and equipment depots, housing and gas factories" used by Kurdistan Workers' Party (PKK) fighters, who have been waging a guerrilla war against the Turkish state since 1984.

Earlier Sunday, the official Turkish news agency Anadolu announced earlier on Sunday that 23 targets -- including bases and arms depots had been destroyed in northern Syria.

Turkey on Saturday said it had hit 54 "targets" in Syria and Iraq belonging to the PKK and the People's Protection Units (YPG).

It came after nine Turkish soldiers were killed the previous day in clashes with suspected PKK fighters at a Turkish military base in northern Iraq.

The PKK is a group that has been blacklisted by Turkey and many of its Western allies as a terrorist organisation.

The YPG is a Syrian Kurdish militia which is a central element of US-allied forces in a coalition against Islamic State.

But Turkey, which claimed its air strikes were in "self-defence", considers the YPG to be terrorists.

Ankara often targets Kurdish fighters in northern Iraq, in the autonomous region of Kurdistan.