The incident has spiked regional tensions caused by the conflict in Syria, where reports Sunday said nearly 40 people died in new clashes between rebels and regime forces.
The jet's wreckage was found in the Mediterranean at a depth of 4,265 feet (1,300 meters), Turkish state media reported Sunday. The two pilots remain unaccounted for.
Turkish Foreign Minister Ahmet Davutoglu said the jet was on a training flight to test Turkey's radar capabilities, not spying on Syria. He said the plane mistakenly strayed into Syrian airspace Friday, but was quickly warned to leave by Turkish authorities and was a mile inside international airspace when it was shot down off the coast of Latakia.
Syria insisted Saturday that the shooting was “not an attack” and that the aircraft had violated its airspace. But Turkish authorities say Syria didn't warn the Turkish plane nor send its own jets to confront it. Turkish Prime Minister Recep Tayyip Erdogan was expected to make a statement Tuesday and might announce some retaliatory steps.
“No one should dare to test Turkey's capabilities,” Davutoglu said Sunday.
Meantime, at the request of Turkey, NATO's governing body will meet Tuesday to discuss the incident, said Oana Lungescu, a NATO spokeswoman. The consultations will focus on article 4 of NATO's founding Washington Treaty.
“Under article 4, any ally can request consultations whenever, in the opinion of any of them, their territorial integrity, political independence or security is threatened,” Lungescu said. The North Atlantic Council—the ambassadors of the 28 NATO countries—will decide whether to respond, she said.
The last time article 4 was invoked was nine years ago—also by Turkey—after tensions with neighboring Iraq escalated. However, that case did not lead to the invocation of article 5, which declares that an attack against any single NATO country shall be considered as an attack against them all.
Despite some opposition leaders' calls for Western military intervention in Syria, the United States and allies have been hesitant to get involved in what could prove a protracted conflict, preferring the diplomatic route. Syrian allies Russia and China have already shielded Syria from U.N. sanctions and stridently oppose any military intervention.
It's unlikely the downing of the Turkish plane will change those calculations, despite Ankara's appeal for the NATO meeting.
In October 1989, two Syrian MiG-21s violated Turkish air space and shot down a Turkish plane on a geographical survey mission, killing all five crew members. Syria at the time promised to severely punish the pilots, who disregarded Turkish orders not to enter Turkish airspace.
Dogu Ergil, a professor of political science at the Ankara University, told private NTV television that Turkey had repeatedly sent its jets across the Syrian border for several weeks to show its military muscle at the time.
Turkey has been one of the most vociferous critics of Syrian President Bashar Assad's regime as it has cracked down over the past 15 months on an increasingly armed popular uprising. Opposition activists say the conflict has killed 14,000 people, most of them civilians.
The plane's downing has already drawn international criticism from other countries pushing Assad to stop his crackdown.
British Foreign Secretary William Hague said Sunday he was “gravely concerned by the Syrian regime's action in shooting down” the plane and that Davutoglu had told him no warning was given.
“This outrageous act underlines how far beyond accepted behavior the Syrian regime has put itself, and I condemn it wholeheartedly,” Hague said in a statement. “The Assad regime should not make the mistake of believing that it can act with impunity. It will be held to account for its behavior.”
Hague met last week with United Nations and Arab League special envoy Kofi Annan for talks on plans for an international summit, while British officials discussed the issue in Geneva on Saturday with members of Annan's team. Hague noted Sunday that “The UK stands ready to pursue robust action at the United Nations Security Council.”
Italy's foreign minister decried the shooting down of the plane as “a further, very grave and unacceptable action by the Assad regime.” In a written statement, Giulio Terzi promised that Italy will play an active role in the NATO meeting Tuesday.
Syrian activists reported violence in different parts of the country Sunday, saying nearly 40 people were killed.
The deadliest incident was in the northern town of Ariha where a shell hit a home killing seven members of the same family, the Britain-based Syrian Observatory for Human Rights said. A video posted online showed the seven men's bodies, some badly mutilated, including one who had part of his head blown off.
Activists also reported intense shelling and clashes between rebels and troops in the eastern city of Deir el-Zour and the central city of Homs, which has been under a government attack for the past two weeks.
Earlier Sunday, activists said rebels captured a military base in the northern Syrian province of Aleppo, confiscating large amounts of ammunition. The Observatory said 16 government troops died in the attacks on the base near the rebel-held town of Daret Azzeh and nearby checkpoints early Sunday.
Area activist Mohammed Saeed said the rebels had removed hundreds of artillery shells from the base. Saeed added via Skype that troops retaliated with intense shelling on the area using helicopter gunships.
On Friday, state media said 25 people were kidnapped by “terrorists” and killed in Daret Azzeh. Activists said the 25 killed were pro-regime gunmen known as shabiha.
Syria's state-run SANA news agency, meanwhile, said gunmen from Turkey clashed with Syrian border guards in Rabiah, a region in the coastal Latakia province. SANA said several infiltrators died in the late Saturday clash, while others reportedly returned to Turkey. It said several Syrian border guards were hurt, but didn't specify how many.
Turkey denies sheltering armed Syrian rebels, although many Syrian refugees have fled to camps on the Turkish side of the border.
Also on Sunday, Syrian opposition groups met in Brussels to hash out differences and plan for a democratic transition. The disparate groups are divided over whether outside military intervention would help or hurt and whether to engage in dialogue with Assad's regime. The conference, attended by some 50 people, will continue Monday.
Jordanian Information Minister Sameeh Maaytah, meanwhile, said Sunday that three other Syrian pilots had defected last week, even before a pilot flew his warplane into neighboring Jordan. He said the other three crossed overland into Jordan. He was unsure if the four pilots knew each other or had coordinated their escape from Syria.