Turkey has ordered residents in the town of Karkamis to evacuate after it was hit by mortars from so-called Islamic State militants in Syria.
Karkamis lies just across the border from Jarablus, an IS-held town which Turkish-backed rebels are expected to try to capture in the coming days.A rebel force is massed in the area and preparing the offensive.
Turkey blames IS for a bomb attack that killed dozens of people in the south of the country at the weekend.
It says the group must now be cleared from the border region, and has been bombarding targets across the border in northern Syria ahead of an expected ground attack.
Turkey's increasing entanglement in Syria's war has added to the strain on its administration and security services following an attempted coup in mid-July.
It accused Fethullah Gulen of masterminding the attempted overthrow from his US home and has dismissed or detained thousands of the cleric's alleged followers. Mr Gulen denies any involvement.
Loudpeaker order
The BBC's Mark Lowen says the decision to evacuate Karkamis is not necessarily a sign that a ground operation is imminent, but a response to the shelling by jihadists.The evacuation order came by loudspeaker, and minibuses were sent in to transport those without cars, he says.
As well as IS forces, Turkey has shelled Syrian Kurdish forces nearby, apparently to deter them from taking Jarablus themselves.
Fifty-four people were killed when the southern city of Gaziantep was hit by a suicide bombing on Saturday.
Our correspondent says the attack on a wedding in the city, blamed on IS, may have been spurred by reports of the imminent Syrian rebel offensive.