A formation of six Turkish fighter jets violated Greek national air space in the northeastern Aegean Thursday, Greek defense officials said.

The Turkish jets entered into Greece’s national air space on one occasion, the defense officials said, adding that two of the aircraft were armed and that one dogfight occurred. In all cases the Turkish jets were chased off by Greek aircraft.

The violations follow a peak in tensions between Turkey and Russia after Turkish fighter jets shot a Russian military jet near the Syrian border.