Turkish Prime Minister Ahmet Davutoglu has said the military has struck Kurdish fighters across the border in northern Syria "twice".

In an interview with A Haber television late on Monday, Davutoglu said Turkey had warned members of the Democratic Union Party (PYD) not to cross to the west of the Euphrates river and if they did, Turkey would attack.

"We struck twice," he said, without giving any further details. Turkey regards the PYD as the Syrian offshoot of the outlawed Kurdistan Workers' Party (PKK) which has waged a bloody insurgency in the Kurdish dominated southeast since 1984.