Turkish presidential sources said the warplane was a Russian-made SU-24.
The Turkish military, which did not confirm the plane's origin, said it had been warned 10 times in the space of five minutes about violating Turkish airspace.
Russia's defence ministry said one of its fighter jets had been downed in Syria, apparently after coming under fire from the ground, but said it could prove the plane was over Syria for the duration of its flight, Interfax news agency reported.
Turkish President Tayyip Erdogan was briefed by the head of the military, while Prime Minister Ahmet Davutoglu ordered consultations with NATO, the United Nations and related countries, their respective offices said.
The Syrian Observatory for Human Rights monitoring group said the warplane crashed in a mountainous area in the northern countryside of Latakia province, where there had been aerial bombardment earlier and where pro-government forces have been battling insurgents on the ground. Both Russia and its ally, Syria's government, have carried out strikes in the area.
A Syrian military source said the reported downing was being investigated. Footage from private Turkish broadcaster Haberturk TV showed the warplane going down in flames in a woodland area, a long plume of smoke trailing behind it.
The plane went down in area known by Turks as "Turkmen Mountain", it said.
Separate footage from Turkey's Anadolu Agency showed two pilots parachuting out of the jet before it crashed.
#BREAKING Warplane crashes in #Syria near #Turkish border. Not clear to which country the plane belonged | via #AA pic.twitter.com/PE1m40Q2Vn — NEW MEDIA NEWS (@HamdiCelikbas) November 24, 2015
Video shows Russian pilot on ground, rebel group says he is dead
A video sent to Reuters by a Syrian rebel group on Tuesday appeared to show a Russian pilot immobile and badly wounded on the ground, and an official from the group said he was dead.
"A Russian pilot," a voice is heard saying as a group of men gather around him. "God is great," a voice is heard saying.
The video was sent to Reuters by a rebel group operating in the northwestern area of Syria, where groups including Free Syrian Army are operating but Islamic State has no known presence.
The official from the group, who declined to be named for security reasons, told Reuters the pilot was dead.
He did not mention a second Russian pilot who was in the plane.
Turkey called this week for a UN Security Council meeting to discuss attacks on Turkmens in neighbouring Syria, and last week Ankara summoned the Russian ambassador to protest the bombing of their villages.
Ankara has traditionally expressed solidarity with Syrian Turkmens, who are Syrians of Turkish descent. About 1,700 people have fled the mountainous Syrian area to the Turkish border as a result of fighting in the last three days, a Turkish official said on Monday.
Russian jets have bombed the area in support of ground operations by Syrian government forces.
(Additional reporting by Daren Butler, Melih Aslan and Asli Kandemir in Istanbul; Maria Kiselyova and Vladimir Soldatkin in Moscow, Tom Perry and Sylvia Westall in Beirut; Writing by David Dolan; Editing by Nick Tattersall, Andrew Heavens and Philippa Fletcher)
