DAMASCUS: Syria accused Ankara of "flagrant aggression" Sunday after Turkish forces shot down a warplane near the border, raising tensions as Syrian loyalists and rebels battled for control of a frontier crossing.
Relations between the neighbouring states have collapsed during the Syrian conflict, with Ankara squarely backing rebels trying to topple President Bashar al-Assad.
It was the most serious incident since Turkish warplanes last September downed a Syrian helicopter that Ankara said was two kilometres (more than a mile) inside its airspace.
A Syrian military source said Turkey shot down the warplane "in a flagrant act of aggression that is evidence of (Turkish Prime Minister Recep Tayyip) Erdogan's support for terrorist groups".
The aircraft "was chasing terrorist groups inside Syrian territory at Kasab", said the source, referring to the disputed border crossing. The pilot was able to eject.
Syrian troops and rebels have been locked in deadly fighting since Friday for control of Kasab border post in the northern province of Latakia, a regime stronghold.
The battle erupted after three jihadist groups, including Al-Qaeda's Syria affiliate Al-Nusra Front, announced the launch of an offensive Tuesday in Latakia dubbed "Anfal", or "spoils of war".
In a move expected to further exacerbate tensions, Erdogan and Turkish President Abdullah Gul praised Turkey's military for downing the warplane.
Erdogan also warned Syria against any response.
"Our response will be heavy if you violate our airspace," he warned Damascus.
The Turkish military said two Syrian MIG-23 planes approaching its airspace were warned "four times" to turn away and that it scrambled fighter jets when one refused to do so and violated Turkish airspace.
A statement said an F-16 jet fired a missile at the Syrian plane in line with "rules of engagement" adopted after a Turkish warplane was downed by the Syrian air force in June 2012, since when Ankara considers any military approach towards the border a threat.
The Britain-based Syrian Observatory for Human Rights said the plane downed on Sunday was bombing rebels fighting to seize Kasab when it was hit.
It said the rebels overran the crossing but were still battling loyalist forces in the area, while activists posted a video on YouTube showing jihadists from Ansar al-Sham flying a black flag over the post.
A Syrian military source denied the fall of Kasab, as a security source said the rebels had infiltrated from Turkey.
The battle for Kasab erupted Friday and at least 80 fighters on both sides have been killed.
Sunday's action prompted an angry response from the foreign ministry in Damascus which, echoing the military source, accused Turkey of "interference" in Kasab and siding with the rebels.
Turkey's "unjustified military aggression against Syrian sovereignty in the Kasab border region over the past two days proves its implication in the events in Syria", it said in a statement.
Turkey "must cease its aggression and support for terrorism", it said, adding however that Damascus "wants good bilateral relations" with Ankara.
According to the Observatory, which relies on a network of activists and medics on the ground for its reports, the fighting in Latakia spread Saturday to a string of villages under regime control.
As a result, "significant military reinforcements have been sent to the government forces", it said.
Latakia province, which includes Assad's family village, is considered a regime stronghold, and many of its residents are from his Alawite minority.
Large parts of the province have remained relatively insulated from Syria's three-year conflict that has reportedly killed more than 146,000 people.
Turkey is a staunch opponent of the Assad government and hosts more than 750,000 refugees, many in camps along the border.
Ankara supports the rebellion against Assad's regime but also worries that jihadists fighting in Syria could threaten its own security.
On Friday, Ankara warned that it would retaliate "in kind" if jihadists in the northern province of Aleppo attack the historic Tomb of Suleyman Shah, which is inside Syria but under Turkish jurisdiction.
Also on Sunday a gunman was killed and 13 were wounded in a firefight between pro- and anti-Damascus factions in Beirut, the latest spillover from the Syria war into Lebanon.