"Turkey's provocative behaviour systematically violates international law, causes great problems to regional stability and security, dynamites attempts to improve Greek-Turkish relations and undermines [Turkey's] European prospects," Spilios Spiliotopoulos said, according to a defence ministry press release.

Sixty Turkish military aircraft entered the Greek Flight Information Region (FIR) on Wednesday without submitting flight plans, the highest activity of the sort noted in 18 months, a Greek army general staff source told AFP.

Sixteen Turkish aircraft violated Greek airspace, and intercepting Greek planes engaged in mock dogfights on three occasions, the source said.

On Thursday, the Greek army general staff reported a further 13 infringements and eight violations of Greek airspace by Turkish planes.

Greek and Turkish officials were scheduled to begin in Athens Friday a 30th round of the closed-door talks the two NATO allies launched in 2002 to resolve their disputes.

Turkish Deputy Foreign Minister Ali Tuygan is already in Athens for the talks, which have so far failed to yield tangible results.