The plane reportedly plunged near Turkey's southern Hatay province. No wreckage has yet been found, the governor says.
A MiG-23 warplane, possibly belonging to the Syrian regime's air force, crashed near Syria's northern border, Turkey said on Saturday evening. The pilot is thought to have bailed out.
Turkey's Prime Minister Binali Yildirim said a search was underway for the pilot, who may have come down on the Turkish side of the frontier.
"It's not clear why the plane crashed. It may be due to weather conditions," he said.
The warplane is believed to have hit the Syrian side.
The Syrian opposition told Anadolu Agency they shot down a plane belonging to the Syrian regime.
Earlier in the day, 11 civilians were killed in air strikes in central Syria, near the ancient city of Palmyra which was recently recaptured by the regime, backed by Russia. The Britain-based Syrian Observatory for Human Rights said Russia was in all likelihood behind the bombing.