ANKARA • Turkish air force planes yesterday downed a drone of unknown origin which had violated Turkey's air space near the Syrian border, the military said.

Russia, whose jets operating in Syria had twice violated Turkish air space this month, insisted all its planes and drones were working as normal after the shoot-down.

The US military believes a drone downed by Turkey was Russian, a US official said yesterday, contradicting Moscow's claims that none of its drones had been lost. "All indications are, yes, it is a Russian drone," the official said, speaking on condition of anonymity. The official added there were no reports of the Syrian army using the type of drone that was shot down.

The Turkish military said the aircraft had been warned three times but had maintained course. It was then "downed by fire from our aircraft on patrol, according to the rules of engagement". The statement did not say if the downed aircraft was manned or a drone. But a Turkish official told the media in Ankara it was an "unmanned aircraft".

NTV television, without citing its sources, also said the object was a drone, and it had fallen 3km inside Turkish territory. Television pictures showed the military examining the drone crash site by the village of Deliosman in the southern Kilis region on the Syrian border.

The state-run Anatolia news agency published pictures of what it said was the downed craft lying upside down in the grass, showing it to be a small vehicle just a few feet long.

Turkey, a key Nato member, had earlier this month complained about two violations of its air space by Russian warplanes operating in Syria.

Turkish Prime Minister Ahmet Davutoglu had warned on Oct 5 after the Russian air space violation that Ankara would activate military rules of engagement irrespective of who violates its air space.

"Our rules of engagement are clear whoever violates our air space," Mr Davutoglu said. "The Turkish armed forces are clearly instructed. Even it is a flying bird it will be intercepted."

However, Russia's military yesterday said that all its planes in Syria had returned safely to base and its drones were "working as normal".

"All the Russian planes in Syria have returned to the Hmeimim airbase after completing their tasks," Defence Ministry spokesman Igor Konashenkov told Russian news agencies. "Russian unmanned aerial vehicles monitoring the situation on the territory of Syria and carrying out air reconnaissance are working as normal."

Turkey supports the moderate opposition in Syria and has been infuriated by Russia's bombing campaign, which Moscow claims is aimed at the Islamic State in Iraq and Syria (ISIS) militants, but which the United States says has been against opponents of Syrian President Bashar al-Assad. Russia said yesterday it had hit over 380 ISIS targets since launching its Syrian bombing campaign on Sept 30.

The Britain-based Syrian Observatory for Human Rights said yesterday it has documented the deaths of 250,124 people, including at least 74,426 civilians, since the conflict in Syria began four years ago.

On Thursday, a US official speaking on condition of anonymity said the US military is poised to boost its supply runs to rebels fighting ISIS in northern Syria, provided the rebels on the ground can prove they are fighting the militants. It followed the Pentagon's announcement last week that it would halt its much-criticised programme to train moderate rebels, and instead focus efforts on equipping pre-screened rebel leaders from those groups actively fighting ISIS.

AGENCE FRANCE-PRESSE