'Syrian' military plane crashes near Turkey border
A plane believed to be a Syrian military aircraft has crashed near the border between Syria and Turkey, Turkish officials say.
A Syrian army source said the air force had lost contact with a fighter jet near the border, state TV reported.
Turkish Prime Minister Binali Yildirim said a search was under way for the pilot, who was thought to have ejected.
An Islamist group which is fighting the Syrian government said the plane had been shot down.
Ahrar al-Sham tweeted a video which it said showed the plane being "targeted".
A spokesman for the group, Ahmed Karaali, was quoted by Turkey's state-run news agency Anadolu as saying the government plane had been bombing Idlib province in northern Syria when it was shot down by opposition forces.
Turkey's prime minister said the plane, which he said was a MIG-23, had crashed near the town of Samandag in Hatay province.
Hatay governor Erdal Ata told Anadolu that rescue teams had arrived at the wreckage and reported that the cockpit was empty.
Mr Yildirim said it was not clear why the plane had crashed. "It may be due to weather conditions," Reuters news agency quoted him as saying.
Turkey supports rebel forces in Syria, which oppose the government of Bashar al-Assad. Turkish military forces also operate on the Syrian side of the border, targeting both Kurdish rebel fighters and so-called Islamic State.
In a separate development, the threat of attack by Turkish-backed rebels has prompted the US-led coalition to increase its military presence around the Syrian city of Manbij.
Kurdish fighters of the Popular Protection Units (YPG) captured Manbij from IS militants in August but the YPG agreed three months later to move its forces east of the River Euphrates.
However, the Kurdish fighters have not moved and Turkey has threatened to attack the city in response, says the BBC's Arab affairs editor, Sebastian Usher.
Pictures have been circulating online of armoured vehicles thought to be from the coalition near Manbij and the coalition spokesman has confirmed that more forces have been deployed.
The spokesman said the increased presence was to deter hostile acts and "keep the focus" on IS.