Turkish fighter jets have forced a Syrian passenger plane to land at Ankara airport on suspicion that it may be carrying weapons, officials and news reports say.

State-run TRT television said the Airbus A320 en route to Damascus from Moscow was intercepted by fighter jets on Wednesday as it entered Turkish airspace and escorted to the capital's Esenboga Airport.

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Ahmet Davutoglu, the Turkish foreign minister, said that the plane was forced to land because of information that it may be carrying "non-civilian cargo".

Interviewed by TRT in Athens, Davutoglu said Turkey was within its rights under international law to investigate civilian planes suspected to be carrying military materials.

The move comes amid heightened tensions between Turkey and Syria, which have been exchanging artillery fire across the volatile border in the past week.

Private NTV television said there were 35 passengers on board the plane.

Syrian airspace 'unsafe'

In a related development, Turkish authorities declared Syrian airspace to be "unsafe" and were stopping Turkish aircraft from flying over the civil-war torn country.

TRT said a Turkish plane that had already taken off for Saudi Arabia made a detour and landed at a Turkish airport on Wednesday.

Earlier in the day, Turkey's military chief pledged to respond with more force to any further shelling from Syria, keeping up the pressure on its southern neighbour a day after NATO said it stood ready to defend Turkey.

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General Necdet Ozel was inspecting troops who have been put on alert along the 910km-border with Syria after a week of cross-border artillery and mortar exchanges escalated tensions between the neighbours, sparking fears of a wider regional conflict.

Turkey has reinforced the border with artillery guns and also deployed more fighter jets to an airbase close to the border region since shelling from Syria killed five Turkish civilians last week.

"We responded and if [the shelling] continues, we will respond with more force,'' the private Dogan news agency quoted Ozel as saying during a visit to the town of Akcakale in Sanliurfa province.

The latest development came as battles between Syrian regime forces and opposition fighters continued across the country on Wednesday.

Ban Ki-moon, the UN secretary-general, urged the Assad's regime to declare a unilateral ceasefire, calls which Syria rejected.

Source: Al Jazeera and agencies