WASHINGTON: The United States on Monday called on all Syria's neighbors to keep a careful watch over their airspace, after Turkey said it had intercepted a Syrian plane from Russia carrying military equipment.

"Certainly we support the decision that Turkey has made in light of the apparent violation of their airspace by this aircraft," State Department spokeswoman Victoria Nuland told reporters.

"We are encouraging all of Syria's neighbors to be vigilant with regard to how their airspace is used, particularly now that we have this concrete example."

Turkish Prime Minister Recep Tayyip Erdogan reiterated Monday that the cargo Ankara confiscated from the intercepted Syrian passenger jet contained weapons, shrugging off Russian claims that the plane carried legal radar equipment.

"It is beyond any doubt that the cargo is war equipment," Erdogan told reporters in Ankara.

The Syrian Air plane traveling en route from Moscow to Damascus was forced by Turkish jets to land in Ankara last Wednesday, reportedly upon intelligence that the civilian plane carried military cargo.

After grounding the plane for nine hours, Ankara announced it seized "objectionable" cargo aboard the plane, triggering a furious reaction from Damascus and its main ally, Moscow.

Nuland stressed however that Turkey was "open to granting humanitarian exceptions" as the conflict in Syria to topple autocratic leader President Bashar al-Assad enters its 20th month, having claimed some 33,000 lives.

Ankara recently "granted approval for an Armenian flight... to overfly Turkey on the condition that it would land and be inspected. It was. It was confirmed to be humanitarian supplies, and they were allowed to go on to Syria," Nuland said.

"So the Turks, from our perspective, are taking a measured and appropriate posture with regard to these things."