Turkey lost a F-4 warplane, similar to the one pictured, over the Mediterranean on June 22, 2012, and Turkey is investigating whether it crashed or was shot down. (OSMAN ORSAL/REUTERS)

Turkey vowed to take “necessary steps” after concluding that Syria shot down a Turkish fighter jet near the Syrian border on Friday, sending tensions soaring in the already fraught region.

In a terse statement issued after an emergency security meeting called by Prime Minister Recep Tayyip Erdogan, the Turkish government said that a missing F-4 fighter jet had been brought down by Syria. The statement said Turkey “will make its final position known once the evidence is fully uncovered and will determinedly take necessary steps.”

On Saturday, Turkish President Abdullah Gul said the investigation would look at whether the plane was shot down in Turkish airspace, Reuters reported, citing Turkish media.

“It is not possible to cover over a thing like this, whatever is necessary will be done,” the state-run Anatolia news agency quoted Gul as saying.

The fate of the jet’s two pilots was not known, and Turkey said that Syrian vessels had joined in a massive search operation in the eastern Mediterranean, where the plane is thought to have gone down. The Turkish military said earlier that it had lost contact with the warplane shortly before noon as it flew over the southern Turkish province of Hatay.

After Turkey, a NATO member, confirmed the shooting, a Syrian military spokesman issued a statement acknowledging that it had shot the plane down at 11:40 a.m., after it approached Syria at low altitude from the sea.

“An unidentified aerial target violated Syrian airspace, coming from the west at a very low altitude and at high speed over territorial waters, so the Syrian anti-air defenses counteracted with anti-aircraft artillery,” said the statement, carried by the official Syrian Arab News Agency. The plane was less than a mile from the Syrian coast when it was hit, and it came down about six miles away, in Syrian territorial waters, the statement said.

The incident underscored the region’s jittery mood as the revolt in Syria degenerates into an armed conflict that many fear will spill beyond its borders, draw in its neighbors and perhaps prompt wider international military intervention.

Compounding the tensions, Turkey has emerged as the main conduit for the new supplies of weaponry that are flowing to Syrian rebels with funds from Saudi Arabia and Qatar and facilitated in part by the United States. More than 30,000 Syrian refugees have flooded into southern Turkey over the past year, and the leadership of the rebel Free Syrian Army is being housed at one of the refugee camps there.

It is not the first time Turkey has been ensnared in the violence since the uprising against President Bashar al-Assad’s rule erupted 15 months ago, souring the once-close relationship between Damascus and Ankara. After Syrian forces fired shots across the border into a camp for Syrian refugees in April, Turkey threatened to invoke a mutual-defense clause in the NATO charter.

Syria seemed eager to play down the plane incident. “There was no aggression,” Foreign Ministry spokesman Jihad Makdissi said on his Twitter account. “It was an unidentified target flying at very low range when it violated Syrian airspace.” He also emphasized the role that Syrian vessels were playing in helping search for the missing pilots.

The shooting nonetheless comes at a moment of heightened concern about the spiraling violence in Syria in the wake of the collapse of a U.N. peace plan brokered by special envoy Kofi Annan. The U.N. monitors who were dispatched to Syria to observe a now-nonexistent cease-fire have been confined to their hotels because it is too dangerous for them to go out, and the Security Council remains divided over what alternatives to pursue.

At a news conference in Geneva, Annan warned that unless the international community agrees on a way forward soon, “it will be too late to stop the crisis from spiraling out of control.”

Among the dozens of deaths reported in Syria on Friday were 25 men who had apparently been executed by rebel forces in a mass killing in the province of Aleppo, according to the Britain-based Syrian Observatory for Human Rights.A video posted on YouTube showed an array of blood-soaked bodies strewn beside a bullet-ridden pick-up on a deserted, unpaved rural road. Some were wearing military fatigues, others jeans and T-shirts. A voice identifies the dead men as “Assad’s shabiha,” a reference to pro-government militias that the opposition blames for much of the violence taking place.

Syria’s state news agency SANA also reported the killings, saying that “armed terrorists” had committed a “brutal massacre” in the Daret Azzeh area of Aleppo, one of several areas in the province that are slipping out of government control.

Special correspondent Suzan Haidamous contributed to this report.