Ankara has previously floated the possibility of setting up a safe haven or humanitarian corridor inside Syria, which would entail military intervention, but has said it would undertake no such action without U.N. Security Council approval.

Turkey has said however that Assad must go.

It was unclear why the Syrians had shot down the aircraft, which, having left a base in Malatya, was flying close to a corridor linking Turkey with Turkish forces on Northern Cyprus.

“The Syrians are clearly quite nervous and are likely to interpret any action, however innocent, as hostile,” said Henri Barkey, an international relations professor at LeHigh University. “Second, reports of Turkish arms support for the insurgents also feeds the paranoia of the regime, understandably.”

It was also possible the air defenses could have mistaken the aircraft for a defecting pilot, following an incident earlier in the week when a Syrian aircraft landed in Jordan.

Russia and China, Assad’s strongest backers abroad, firmly oppose any outside interference in the Syrian crisis, including foreign arming or funding of insurgents, saying envoy Kofi Annan’s stalled peace plan is the only way forward.

Assad’s prime minister, appointed after a parliamentary election conducted last month despite the violence convulsing the country, named a new cabinet on Saturday, retaining the same interior, defense and foreign ministers.