Turkey's air force has shot down a Syrian aircraft for violating Turkish airspace, an action that Syria denounced as "unprecedented and unjustifiable".
The incident happened on Sunday, with the plane crashing near the Syrian town of Kasab on the Turkish border after it was targeted by F-16s.
The Turkish prime minister, Recep Tayyip Erdogan, praised the Turkish military for the action.
During an election rally in the northwest of Turkey, Erdogan said: "A Syrian plane violated our airspace. Our F-16s took off and hit this plane. Why? Because if you violate my airspace, our slap after this will be hard.
"I congratulate the chief of general staff, the armed forces and those honourable pilots... I congratulate our air forces," he told supporters.
The Syrian state news agency SANA reported the Foreign Ministry as protesting against Turkish "interference" in the province of Latakia, which has witnessed heavy fighting in recent days.
In a statement the ministry said Turkey's "flagrant aggression against Syrian sovereignty in the Kasab border region over the past two days proves its implication in the events in Syria".
The Latakia province includes President Bashar al-Assad's family village of Qardaha.
The Syrian Observatory for Human Rights, a UK-based anti-Assad monitoring group, said the plane had been striking areas in Latakia in pursuit of rebels trying to gain control of a border post.
Syria and Turkey have been at odds over the civil war, with cross-border fire and the deployment of missiles exacerbating tensions between the two countries.
Al Jazeera's diplomatic editor James Bays, speaking from Kuwait ahead of Tuesday's Arab League summit, said the shooting was "an important incident".
"The Arab League ministers will be aware of this and following reports quite closely. This is not just one of Syria's neighbours, this is a member of NATO. We should remember June 2012, when Turkey had their jet shot down. It could have changed the conflict completely but it didn't.
"The next few days will be a sensitive period. We need to see how the Syrian government is going to react."
A statement from the Turkish military on Sunday said that two Syrian MIG-23 aircraft flew towards the Turkish border on, leading to four warnings being issued.
One aircraft heeded the warnings and changed course, while the other flew for about 1.5km in Turkish airspace. Damascus maintains that its aircraft were in Syrian airspace.