Turkey launched a military operation against Kurdish fighters in north-east Syria, with air strikes hitting the border town of Ras al Ain.
President Recep Tayyip Erdogan said on his official Twitter account that the operation, named «Peace Spring,» had begun.
He said the operation aims to eradicate «the threat of terror» against Turkey.
@RTErdogan: The Turkish Armed Forces, together with the Syrian National Army, just launched #OperationPeaceSpring against PKK/YPG and Daesh terrorists in northern Syria. Our mission is to prevent the creation of a terror corridor across our southern border, and to bring peace to the area.
Turkey had been poised to advance into north-east Syria since US troops began vacating the area in an abrupt policy shift by US President Donald Trump, widely criticised in Washington as a betrayal of America’s Kurdish militia allies.
Mr Trump announced the decision after a phone call with Mr Erdogan on Sunday evening (local time).
World powers fear the action could open a new chapter in Syria’s war and worsen regional turmoil.
Turkey has said it intends to create a «safe zone» in order to return millions of refugees to Syrian soil.
A spokesman for the US-backed Kurdish-led force in northern Syria said Turkish warplanes have started targeting «civilian areas» in northern Syria.
Mustafa Bali of the Syrian Democratic Forces said the airstrikes have caused «a huge panic among people of the region».
Mr Erdogan earlier told Russia’s President Vladimir Putin in a phone call that the operation would help peace and stability in Syria.
But Syria said it was determined to confront any Turkish aggression by all legitimate means.
Turkey views Kurdish YPG fighters in north-east Syria as terrorists because of their ties to militants waging an insurgency inside Turkey, an influx of non-Kurdish Syrians would help it secure a buffer against its main security threat.
More to come.