Syrian military says it has shot down Turkish fighter jet "over its territorial waters", risking a new crisis between Middle Eastern neighbours already at bitter odds over a 16-month-old revolt against Syrian President Bashar al-Assad.
"Our air defences confronted a target that penetrated our air space over our territorial waters pre-afternoon on Friday and shot it down. It turned out to be a Turkish military plane," a statement by the military circulated on state media said.
Turkish Prime Minister Recep Tayyip Erdogan's office in a statement confirmed the incident in which two pilots went missing.
"As a result of information obtained from the evaluation of our concerned institutions and from within the joint search and rescue operations with Syria, it is understood that our plane was brought down by Syria," Erdogan's office has said in a statement.
Turkey would decide on its response to the incident once all of the details became clear, it said in the statement, issued after a two-hour meeting between Erdogan, members of his cabinet and the military.
Al Jazeera’s Anita McNaught, reporting from Istanbul, said: "What those necessary measures are in Turkey’s views, whether it will be taking it alone or invoking its membership of NATO or calling for wider support, we don’t know."
"Beyond that what was Turkish fighter bomber plane was doing in Syrian airspace in the first place as per Turkish military," she said.
"We don’t know how the plane was downed and how the international community is going to support Turkey in whatever response it decides to take."
The military has said a search and rescue operation for the two pilots of the F-4 plane was under way, the Anatolia state news agency said.
'Escalation in tensions'
The jet had lost radio contact with its base over the eastern Mediterranean near Syria's Latakia, an army statement said earlier.
Ankara had said earlier that it had lost contact with one of its military aircraft off its southeastern coast after it took off from Erhac airport in the eastern province of Malatya.
NATO-member Turkey, which had drawn close to Syria before the uprising against Assad, turned against the Syrian leader when he responded violently to pro-democracy protests inspired by popular upheavals elsewhere in the Arab world.
Ankara has previously floated the possibility of setting up some kind of safe haven or humanitarian corridor inside Syria, which would entail military intervention, but has said it would undertake no such action without UN Security Council approval.
Al Jazeera's McNaught said: "This is a dramatic escalation in tensions between two neighbouring countries. Relations have been bad for many months and the worse was when Syrian army fired on Turkish refugee camp holding Syrian refuges."
"At that point Turkey invoked issues of national sovereignty; it was seen as a bit of over-reaction then.
"We are in a completely different territory now."
Russia and China, Assad's strongest backers abroad, have fiercely opposed any outside interference in the Syrian crisis, saying envoy UN and Arab League envoy Kofi Annan's peace plan is the only way forward.
Russian Foreign Minister Sergei Lavrov said after talks with his Syrian counterpart that he had urged Syria to "do a lot more" to implement Annan's proposals, but that foreign countries must also press rebels to stop the violence.
Lavrov said the Syrian authorities were ready to withdraw troops from cities "simultaneously" with opposition fighters.
A Syrian military pullback and a ceasefire were key elements in Annan's six-point peace plan.
Annan hit out at some countries he said had taken national initiatives that risked unleashing "destructive competition".
He told a news conference in Geneva on Friday that he wanted states with influence on both sides of the conflict to be involved in the peace process, including Iran, Assad's closest ally.
Annan was speaking a week before a planned Syria crisis meeting that is in doubt because of Western objections to the Islamic Republic's participation.