The strikes came after a Syria war monitor said Turkish drone strikes had killed 27 civilians in Syria in a 24-hour military escalation, after an attack on Wednesday at state-run Turkish Aerospace Industries (TAI) near Ankara, which Turkey said killed five people.

After the Ankara attack, Turkey's defence ministry had announced strikes against sites linked to the PKK in Iraq and Syria.

"A series of Turkish air strikes targeted the Sinjar Resistance Units," a security official told AFP, reporting a total of five people killed, as the PKK claimed Wednesday's attack.

The official spoke from Nineveh province, where Sinjar is located, under cover of anonymity because he was not authorised to brief the media.

Speaking under similar ground rules, a second official in Sinjar gave the same toll for the "Turkish aerial bombardments targeting positions of the Sinjar Resistance Units".

In a statement, the anti-terrorist service of Iraq's autonomous Kurdistan region, adjacent to Nineveh, gave a lower toll of "three fighters killed" in Sinjar.

It said the strikes by Turkish drones and warplanes targeted PKK positions.

Turkey frequently carries out ground and air offensives on positions of the PKK -- which has waged a decades-long insurgency against the Turkish state -- in northern Iraq, the autonomous Kurdistan region and the mountains of Sinjar.

Turkey has also over the past 25 years operated several dozen military bases in northern Iraq in its war against the PKK.