Turkey scrambled six F-16 fighter jets in three separate incidents responding to Syrian military helicopters approaching the border on Sunday, its armed forces command said yesterday.

It was the second time in as many days Turkish jets were launched in response to Syrian helicopters flying near the border and comes after a Turkish reconnaissance plane was shot down by Syria late last month.

The jets took off from Incirlik air base in southern Turkey after Syrian helicopters were spotted flying south of the Turkish province of Hatay, the chief of general staff said on the military's website.

Turkey has beefed up its troop presence and air defences along the southern border after Syria shot down one of its jets over the Mediterranean on June 22.

The incident prompted a sharp rebuke from Ankara, which said it would respond "decisively".

Turkish Prime Minister Tayyip Erdogan said the military's rules of engagement had been changed and that any Syrian element approaching Turkey's border and deemed a threat would be treated as a military target.

Syria says it shot down the jet in self-defence and that it was brought down in Syrian air space. Turkey says the jet accidentally violated Syrian air space for a few minutes but was brought down in international air space.

While the incident has heightened tension between the once-close allies, neither Turkey, which fears a local clash escalating into a regional sectarian conflict, nor Syria has any interest in a confrontation on their shared border.

Turkey has become increasingly vocal against Syrian President Bashar al Assad, calling for him to step down, and has given sanctuary to rebels opposing the Syrian leader.

Meanwhile, Turkey's armed forces command said it had carried out air strikes on three militant targets belonging to the Kurdistan Workers Party, which is fighting for greater Kurdish autonomy in Turkey.