Firemen put out a blaze at a power station in Qamishli on Monday as Turkey carried out airstrikes against Kurdish sites in northeastern Syria and northern Iraq. AFP

Turkey's military carried out airstrikes against Kurdish militants in northern Iraq and Syria on Monday night, destroying 23 targets, the defence ministry said, sustaining an escalation of conflict south of the country's border.

The upswing in violence began on Friday when nine Turkish soldiers were killed in clashes with Kurdistan Workers Party (PKK) militants in northern Iraq, prompting Ankara to conduct airstrikes and operations both there and in northern Syria.

The latest airstrikes were carried out late on Monday in the Metina, Gara, Hakurk and Qandil regions of northern Iraq as well as in northern Syria to ensure border security and prevent attacks, the ministry said.

"Twenty-three targets were destroyed, including caves, shelters, tunnels, ammunition warehouses, supply materials and facilities used by the terrorist organisation," it said in a statement accompanied by a photo of Turkish warplanes.

It said many militants were "neutralised", a term commonly used to be mean killed.

The PKK, designated a terrorist group by Turkey, the United States and the European Union, took up arms against the Turkish state in 1984. More than 40,000 people have been killed in the insurgency.

Turkish forces regularly strike PKK militants based in the mountains of northern Iraq.

Kurdish Syrian firemen put out a blaze at a power station in Qamishli after targeted by Turkish drones on Monday. AFP

Earlier, Syrian state media and other sources said on Monday that Turkey had carried out a wave of airstrikes on electricity and oil infrastructure in Syria's Kurdish-held northeast, putting several power stations out of service.

Turkey has carried out a series of military incursions and bombing campaigns in Syria against the Kurdish YPG militia, which it regards as a wing of the PKK.

Turkish authorities said on Monday that police had detained 18 people for "praising terrorism" after Friday's killing of the Turkish soldiers, while a high-level PKK member was "neutralised" in northern Iraq.

There was no immediate reaction from the PKK, which seldom confirms attacks against it.

Reuters