ANKARA - Turkey summoned the Russian ambassador to Ankara for a second time after a new violation of its air space by a Russian warplane close to the Syrian border, a Turkish foreign ministry official said on Tuesday.
"The Russian envoy was summoned for a second time yesterday (Monday) afternoon to strongly protest another violation of Turkish air space on Sunday," the official told AFP on condition of anonymity.
Turkey warned the Russian envoy that similar incidents should not happen again otherwise "Russia would be held responsible," the official said.
The violation on Sunday appears to have been the second in as many days after Turkey said its fighter jets intercepted a Russian warplane close to the Syrian border on Saturday, forcing it to turn back.
The Russian ambassador had also been summoned following Saturday's incident.
Turkish Prime Minister Ahmet Davutoglu on Monday warned that Ankara would activate military "rules of engagement" irrespective of who violates its airspace.
"Even if it is a flying bird it will be intercepted," Davutoglu said in an interview with Turkish television.
The Turkish military said on Monday that two Turkish F-16 jets were harassed by an unidentified MIG-29 aircraft on the Syrian border on Sunday.
"Two F-16 jets were harassed by a MIG-29 plane - whose nationality could not be identified - for a total of five minutes and 40 seconds," the army said in a statement.
It was not immediately clear if the incidents on Sunday referred to by the army and the foreign ministry were the same episode or separate.
Russian warplanes have been flying over Syrian territory since Wednesday, conducting air strikes on what Moscow says are targets belonging to Islamic State (IS) group jihadists and other "terrorist" groups in the country's northern and central provinces.
The West has accused Moscow of using the raids as cover to hit President Bashar al-Assad's moderate opponents.
Turkey and Russia remain on opposing sides of the Syrian conflict, with Moscow one of the few allies of Assad while Ankara says his ouster is the only way out of the current stalemate.
Ankara and Moscow enjoy burgeoning trade ties and had until recent months appeared intent on building a strong strategic alliance.
After an emergency meeting on Monday, NATO called on Russia to "immediately cease its attacks on the Syrian opposition and civilians" and also warned against violating Turkey's airspace.
The military alliance said in a statement that the allies "note the extreme danger of such irresponsible behaviour." US Secretary of State John Kerry warned Monday that a Russian "incursion" into the air space of Washington's NATO ally Turkey risked provoking a serious escalation.
"It is precisely the kind of thing that had Turkey responded under its rights could have resulted in a shoot-down," he said, at a public event in Chile.