NATO member states have condemned Syria for its shooting down of a Turkish military jet, calling it "unacceptable" and demanding that Damascus take steps to prevent further incidents.

Ambassadors of NATO's 28 member states met in Brussels to consult with Turkey on the incident on a request from Turkey.

NATO Secretary-General Anders Fogh Rasmussen said NATO security was "indivisible".

NATO condemned it "in the strongest terms," Secretary General Anders Fogh Rasmussen said after the alliance met Tuesday at Turkey's request.

Rasmussen refused to comment on what intelligence Turkey had presented to NATO about the incident at the allliance's headquarters in Brussels, Belgium, as cited by CNN.

He called on Syria to "avoid such events in the future" and said he did not expect the situation to escalate.

NATO did not promise any action in response to the incident, and Turkey did not invoke the NATO article calling for collective defense of members, Rasmussen said.

However, he said NATO's Article 5, which calls for member states to see an attack on one country as an attack on all the alliance's members, had not been discussed.

Damascus said the shooting down was self-defense but Ankara branded the incident an "act of aggression".

The United States and many other countries have been vocally opposed to military intervention in Syria and are unlikely to encourage Turkey to press the issue. After Syrian troops shelled refugees on the Turkish side of the border earlier this year, Secretary of Defense Leon Panetta made clear that the bar was high for Turkey to claim the need for a collective self-defense.

Syria raised the stakes Monday in the war of words over the incident.

Syrian Foreign Ministry spokesman Jihad Makdissi said the plane was shot down in Syrian airspace, disputing Turkey's claim that it was downed over international waters after briefly straying into Syrian airspace by mistake.

"What happened was a violation of Syrian airspace. Even Turkey says Syrian sovereignty was violated. Regardless of whether it was a training mission, a reconnaissance mission, it was a violation," Makdissi said.

He insisted that Syria was the wronged party, not Turkey.

It is only the second time in NATO's 63-year history that it has convened under Article 4 of its charter.

The first time was in 2003 to discuss the Iraq war, again at the request of Turkey.

Article 4 provides for consultations when a member state feels its territorial integrity, political independence or security is under threat.

By invoking Article 4 of the NATO charter, rather than Article 5 which calls for military action, Turkey has signalled it wants action against Syria short of armed intervention.