Turkey said it had downed a Syrian military helicopter that violated its airspace on Monday, in a move Damascus said was aimed at heightening tensions between the former allies.
The Syrian MI-17 helicopter was detected two kilometres (1.2 miles) inside Turkish airspace and shot down five minutes later after failing to heed warnings, Turkish Deputy Prime Minister Bulent Arinc told reporters.
"It was continuously warned by our air defence but as the violation continued, it fell on Syrian soil at 2:25 pm (1125 GMT), having been hit by missiles from our planes," which took off from their base in the eastern province of Malatya, he said.
Arinc added that there was no information about the fate of its crew because the helicopter fell on Syrian soil.
Syria's army hours later confirmed the helicopter had been shot down by Turkey, accusing Prime Minister Recep Tayyip Erdogan of trying to "escalate" tensions between the two countries.
The downing of the helicopter comes at a time of heightened diplomatic activity to resolve the Syrian crisis, which has spillover effects across the region.
Arinc said that Turkey has changed its military rules of engagement in response to repeated gunfire from the Syrian side towards the border areas in recent months.
In a statement posted on its website, the Turkish military said the Syrian helicopter was detected when it was 26 nautical miles away from its airspace and was warned until it was five nautical miles away.
"Despite that, the Syrian helicopter kept on approaching the Turkish airspace," the army said, adding that it violated the airspace in the vicinity of the Guvecci border post, while it was flying at an approximate altitude of 14,200 feet.
One of the two patrolling Turkish F-16 jets shot down the helicopter which fell almost one kilometre inside Syrian territory, according to the army.
Turkey has also notified in writing the United Nations and NATO, a Turkish official said.
"It is only natural to notify NATO of the incident because an armed action was involved," the official told AFP on condition of anonymity.
Foreign Minister Ahmet Davutoglu said Turkey exercised its rights under international law and was determined to protect its borders.
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"From now, nobody will dare to violate Turkey's borders. All measures have been taken," Davutoglu said in televised remarks during a visit to Paris where he attended a meeting about Syria with his US, British, French and Saudi counterparts.
Syria's army published a statement in which it said a military helicopter was "lost... while it was on a reconnaissance mission to monitor the infiltration of terrorists via the Turkish border."
Damascus has frequently accused Ankara of financing, training and allowing jihadists fighting alongside Syria's rebels to cross the border to join the war.
The televised statement added that the helicopter was "targeted directly by Turkish warplanes."
"Given that the helicopter was on its way back and that it was not on a combat mission, the hasty Turkish reaction is proof of the true intentions of Erdogan's government towards Syria, which are to create tension and escalate the situation at the border between the two countries," it added.
The incident occurred as the UN Security Council is expected to start negotiations this week on a resolution to back a US-Russian plan to destroy Syria's chemical stockpile.
A cautious Turkey welcomed the US-Russian accord but warned that Damascus could be seeking to buy more time for its deadly military campaign.
The long Turkish-Syrian border has become increasingly tense. More than 500,000 refugees have fled the fighting in Syria.
Relations have deteriorated between Damascus and Ankara, who were once close allies, since the outbreak of an uprising against Syrian President Bashar al-Assad and the unleashing by the regime of a brutal crackdown against dissent in March 2011.
Turkey has consistently lobbied for the ouster of Assad and provided shelter for Syrian rebels seeking to overthrow the embattled leader.
Earlier on Monday, the Syrian Observatory for Human Rights monitoring group reported that a Syrian military helicopter had crashed near the Turkish border.
Observatory director Rami Abdel Rahman said the helicopter had landed on the Syrian side of the border and that rebel fighters had captured one of its two pilots.
The second pilot's fate is unknown, he said.