* Syria calls Turkish reaction "hasty"
* Turkish deputy PM says helicopter had been warned
* Helicopter crashes in Syrian territory
By Saif Tawfiq
YAYLADAGI, Turkey, Sept 16 (Reuters) - Turkey said its warplanes shot down a Syrian helicopter on Monday after it crossed into Turkish airspace and the government warned it had taken all necessary measures to defend itself against any further such violations.
Turkey scrambled two F-16 jets along the border between its southern Hatay province and Syria after warning the Mi-17 helicopter it was approaching Turkish airspace shortly before 2:30 p.m. (1130 GMT), the military said in a statement.
Syria called the reaction "hasty" and accused Turkey of trying to escalate tensions along the border.
Deputy Prime Minister Bulent Arinc said a warplane shot down the helicopter after it ventured up to 2 km (1 miles) into Turkey near the border town of Yayladagi. "It was repeatedly warned by our air defence elements," he said.
It came down in a ball of flames inside Syrian territory after being hit, amateur video footage showed.
"Turkey will definitely not allow any violation of its borders ... We will defend our borders and our people's security to the end," Turkish Foreign Minister Ahmet Davutoglu told reporters in Paris.
"No one will have the nerve to violate Turkey's borders in any way again," he said after a meeting to discuss Syria with U.S. Secretary of State John Kerry, British Foreign Secretary William Hague and their French counterpart Laurent Fabius.
Davutoglu said details of the incident would be provided to U.N. Secretary-General Ban Ki-moon and the U.N. Security Council and fellow members of the NATO military alliance.
Syria's army acknowledged the helicopter had strayed into Turkish airspace for a short time while monitoring "terrorists" moving across the border into Syria, but said it was an accident and that the aircraft was on its way back when it was shot down.
In a statement carried by state news agency SANA, it accused Prime Minister Tayyip Erdogan's government of trying to increase tensions between the two countries.
"The hasty response from the Turkish side, especially as the aircraft was on its way back and was not charged with any combat missions, is proof of the true intentions of Erdogan's government toward Syria to increase tensions and escalate the situation on the border between the two countries," it said.
Turkey, one of Syrian President Bashar al-Assad's fiercest critics, has advocated military intervention in Syria and grown frustrated over what it sees as Western indecisiveness.
It shares a 900-km (560-mile) border with Syria and is sheltering a quarter of the 2 million people who have fled the Syrian conflict.
Turkish financial markets have been nervous about the prospect of outside intervention in Syria, fearing Turkey could be drawn into an escalating conflict.
The Turkish lira, which had earlier strengthened to below 2 to the dollar for the first time in almost three weeks partly on hopes for diplomacy over Syria, briefly weakened back above 2 on the news.
Following Syria's downing of a Turkish jet in 2012, Erdogan said the military's rules of engagement had changed and that any Syrian element approaching the border would be deemed a threat and be treated as a military target.
Turkey has bolstered its defences and deployed additional troops on its border with Syria in recent weeks, with convoys of military vehicles ferrying equipment and personnel and additional short-range air defences set up.
Its armed forces have frequently responded in kind to stray gunfire and mortar rounds hitting its territory and it is hosting six NATO Patriot missile batteries meant to defend it against any attacks from Syria.