Syria shot down a Turkish warplane over the Mediterranean yesterday, risking a new crisis between Middle Eastern neighbors already at bitter odds over a 16-month-old revolt against Syrian President Bashar Assad.

Turkish Prime Minister Tayyip Erdogan said Syria had admitted it had shot down the plane and apologized, BBC Monitoring reported, citing Turkey’s state news agency Anatolia.

Turkey said earlier 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.

Turkish officials said Erdogan, who was returning to Ankara from Brazil yesterday evening, would convene a security meeting with the interior and foreign ministers and the chief of general staff. They did not say what would be discussed.

Turkey’s military said a search and rescue operation was under way. Two crew were aboard the F-4 jet, Anatolia said.

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. Russia and China, Assad’s strongest backers abroad, have fiercely opposed any outside interference in the Syrian crisis, saying 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 UN-backed 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 rebels. A Syrian military pullback and a cease-fire were key elements in Annan’s six-point peace plan, most of which remains a dead letter.

Violence raged on unabated in Syria, which appears to be sliding toward a sectarian-tinged civil war

Rebels killed at least 25 members of a pro-Assad militia, and in a separate incident troops turned heavy machine guns on opposition demonstrators in the northern city of Aleppo, killing 10, opposition activists said.

“Armed terrorist groups committed a brutal massacre against 25 citizens in Darat Azzah,” state TV reported, saying more were missing from the village in Aleppo province.

Several men covered in blood and piled on top of each other on a roadside, some in army fatigues and some in t-shirts, could be seen in a video link sent by the Syrian Observatory for Human Rights, apparently showing the aftermath of the same incident. The British-based opposition watchdog said 26 men believed to be pro-Assad “Shabbiha” militiamen had been killed.

Assad’s foes have accused troops and Shabbiha militiamen of perpetrating many abuses against civilians, including mass killings, in the uprising that began in March last year with peaceful protests against four decades of Assad family rule.

In Aleppo, Syria’s business hub, thousands of demonstrators were marching toward the central Saadallah Al-Jabiri Square when four armored vehicles fired on them, activists told Reuters by telephone. Two of them said they were speaking from Aleppo.

“The wounded were taken to houses and are trapped there. They cannot be transported to hospitals because troops and Shabbiha are surrounding the neighborhood,” one of them said.

Aleppo, along with central Damascus, had stayed relatively quiet in the early months of the revolt that engulfed many other provincial cities, but unrest has gradually spread there too.

Activist video footage showed a large crowd of protesters, some draped in revolutionary flags, running along a street as heavy gunfire cracked out. Another video showed a man whose chest was covered in blood being dragged along the road.