Turkey said its warplanes shot down a drone Friday near its border with Syria, underscoring heightened hostility in the region’s increasingly crowded airspace.

The aircraft was warned three times to turn back before being fired on by Turkish jets patrolling the border, the Turkish military said in a statement. It gave no further details.

Russia, which sent military planes into Syria last month, said none of its aircraft in Syria had been hit. But the United States suspected that Turkish fighters targeted a Russian drone, the Reuters news agency reported, citing a U.S. official speaking on the condition of anonymity.

The incident occurred during a period of escalating tension along the Syrian border since Russia began an air campaign in support of President Bashar al-Assad 2 1/2 weeks ago. Turkey, a NATO member, has accused Russia of intentionally violating its airspace on two occasions since then. The incidents have drawn sharp rebukes from Turkey’s NATO allies.

“Our aircraft performing patrol duty on the border fired and shot down the aircraft,” the Turkish military statement said. It said Turkey acted “within the rules of engagement.”

The drone went down near the village of Deliosman, in Kilis province, Turkish media reported. The province borders Syria’s Aleppo province, where Syrian government forces, backed by Russian airstrikes, launched a new offensive Friday.

Turkish Foreign Minister Feridun Sinirlioglu said the drone crossed the border and flew nearly two miles into Turkey before it was shot down. Some of the wreckage was examined, and photos of the downed drone were circulated by the Turkish media.

The wreckage resembled that of a small Russian-made Orlan-10 reconnaissance drone, reported the Aviationist, a blog specializing in military aviation.

The United States, Russia and Syria operate drones in the border region.

In Moscow, Maj. Gen. Igor Konashenkov, a spokesman for the Russian Defense Ministry, said no Russian aircraft had been shot down. “All the airplanes of the Russian aviation group in the Syrian Arab Republic have returned after accomplishing their combat tasks,” Konashenkov said.

In Lebanon, the pro-Syrian al-Mayadeen television channel echoed that denial, quoting a Syrian military official as saying that no Syrian or Russian warplane or drone had been shot down over Turkey.

The alliance between Russia and the regime of Bashar al-Assad goes back decades. Here's a bit of historical context that explains why Russia is fighting to prop up its closest ally in the Middle East. (Ishaan Tharoor and Jason Aldag/The Washington Post)

Since 2013, Turkey has downed a Syrian military jet, a helicopter and a surveillance drone that crossed into Turkish airspace. Turkey announced that any aircraft entering its airspace from Syria would be considered a threat after Syrian ground fire brought down a Turkish F-4 Phantom II fighter jet in 2012.

The United States, which is leading separate airstrikes against the Islamic State, has raised concerns about possible confrontations between Russia and Turkey in the skies over Syria.

Defense Secretary Ashton B. Carter this month called on Russia to act in a “safe and professional manner” and respect Turkish sovereignty. NATO Secretary General Jens Stoltenberg said last week that the organization has “a duty to reinforce” its member state after the incursions, which he described as unacceptable.

NATO said Friday that Turkey has not asked it for help since the aircraft was downed.

“We understand that Turkish authorities are investigating the origin of the unidentified drone that was shot down. Turkey has not asked for any NATO assistance or consultations,” said a NATO spokesman, who spoke on the condition of anonymity under customary ground rules.

In an attempt to ease friction with Turkey over previous warplane incursions, a high-level Russian military delegation held talks in Ankara on Thursday. Russia has blamed bad weather for what it says was a single incursion, and Turkey said it received apologies from the Russians.

“They apologized a few times, said it happened by accident and that they have taken measures so that it will not occur again,” Sinirlioglu, the foreign minister, said following the meetings, Reuters reported.

Russian airstrikes have added new zeal to the beleaguered Syrian government’s campaign. The Syrian army advanced to control four towns south of Aleppo on Friday, the state-run Syrian Arab News Agency reported. A U.S. defense official and Syrian activists said this week that hundreds of Iranian troops were among those massing for an offensive near Aleppo. Pro-government forces have also launched attacks near the central city of Hama.

Michael Birnbaum in Brussels, Erin Cunningham in Cairo and Thomas Gibbons-Neff and Brian Murphy in Washington contributed to this report.

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