UPDATED: 1:35 p.m. ET
Turkey shot down a Russian Sukhoi Su-24 military plane near its border with Syria on Tuesday and rebels on the ground shot and killed one of the pilots as he parachuted to the ground, contributing to an immediate intensification of tensions in the region.
Russia said the plane had stayed above Syria while Turkey said it had encroached upon Turkish airspace, and that it warned the Russian plane "10 times in five minutes" about the airspace violation before two Turkish F-16s shot it down.
Turkmen rebels in Syria claimed responsibility for shooting dead both Russian pilots after they ejected from the plane as it plunged towards the ground near the Syrian border with Turkey, though Russia hasn't confirmed the fate of the second pilot.
"Both of the pilots were retrieved dead. Our comrades opened fire into the air and they died in the air," Alpaslan Celik, a deputy commander in a Syrian Turkmen brigade told Reuters reporters. He was speaking from an area near the Syrian village of Yamadi as he held what he said was a piece of a pilot's parachute.
The Russian defense ministry confirmed that the first pilot was killed and that a second "soldier" was killed in a rescue operation. General staff spokesman Lt. Gen. Sergei Rudskoi said the pilot was killed by ground fire as he parachuted from his crippled plane, while rebels fired on a Russian helicopter that was searching for the two pilots, killing one crew member and forcing the helicopter to land in neutral territory.
Speaking on Russian TV, Russian President Vladimir Putin called the downing of the jet a "stab in the back by the accomplices of terrorists" and said it would have "serious consequences for Russian-Turkish relations."
This is the first time a Russian or Soviet plane has been shot down by a NATO member since the 1950s, according to Reuters. Russia's defense ministry said the plane stayed exclusively within Syrian airspace and was at an altitude of 6,000 meters when it was shot down, presumably from ground fire, according to Russian news agency TASS.
An unconfirmed video circulating online and viewed by Mashable purportedly showed a Russian pilot unconscious on the ground and surrounded by armed men, who appeared to be celebrating. It was unclear whether he was alive or dead at the time it was filmed. (Warning: Graphic content in video.)
The plane went down in the mountainous Jabal Turkmen area of the Latakia region, according to the UK-based Syrian Observatory for Human Rights. Air strikes and fighting between rebels and Syrian government forces had been reported earlier in the day.
Footage from Turkey's Anadolu Agency reportedly showed a pilot parachuting out of the aircraft as it falls.
The Turkish military said Turkish officials released a radar map that allegedly proves the plane violated Turkish airspace.
Supposed radar tracks of RuAF Su-24 shot down released by @CNNTURK_ENG #SyriaCrisis #Russia #Turkey pic.twitter.com/7c3ZWTIHj0— Ian Keddie (@IanJKeddie) November 24, 2015
Russian President Vladimir Putin's spokesman Dmitry Peskov called the downing of the plane "a very serious incident," but said it is too early to draw any firm conclusions.
Russia began air strikes in Syria in late September. Though Moscow said it was targeting Islamic State (IS) extremists, there have been widespread reports that the strikes seem to target areas controlled by more moderate rebel groups fighting against the regime of Syrian President Bashar al-Assad -- a Russian ally in the Middle East.
Turkey, a member of NATO, shot down an unidentified drone that had violated its airspace at the border with Syria in October. It had complained about Russian warplanes violating its airspace earlier in the month.
A NATO spokesman told Mashable that they are closely monitoring the situation and are in contact with Turkish authorities. He wouldn't confirm whether this would be the first such military incident between a NATO member and Russia, but pointed to incursions by Russian aircraft onto Turkish airspace on Oct. 3 and Oct. 4.
Speaking later on Tuesday, NATO Secretary-General Jens Stoltenberg called on all parties to be prudent and to contribute to reducing tensions. Stoltenberg said the situation is serious, but that he hopes for renewed contacts between Turkey and Russia.
He said the assessments of other NATO members supported the Turkish version of events.
Putin is meeting on Tuesday with King Abdullah of Jordan, the Sputnik news agency said.
UPDATES:
6:35 p.m. GMT, comments from NATO, confirmation of pilot's death
3:20 p.m. GMT, detail on pilots
2:45 p.m. GMT, added detail on pilots
1:05 p.m. GMT, added Putin's comments
12:45 p.m. GMT, detail on NATO incidents
12:15 p.m. GMT, on pilot's suspected death
12:00 GMT, with video link
11:40 a.m. GMT, with Russia defense ministry statement, radar map and more details
10:35 a.m. GMT, with NATO and Kremlin statement
Megan Specia contributed to this article.