Turkey sent fighter jets to its southeastern frontier with Syria for a second day on Thursday, a Reuters witness said, following an air assault this week by Syrian warplanes on the rebel-held border town of Ras al-Ain.
A Reuters reporter in the Turkish town of Ceylanpinar, which abuts Ras al-Ain, said he saw two Turkish jets roar along the frontier.
He said there was no sign of fighting in Ras al-Ain, after days of bombing by forces loyal to President Bashar al-Assad.
Rebels overran the town last week during an advance into Syria's mixed Arab and Kurdish northeast that has triggered some of the biggest refugee movements of the 20-month civil war.
Turkey has promised to defend itself against any spillover of violence from its neighbour, and says it has fired back repeatedly in retaliation for stray gun and mortar fire landing on its soil.
Reuters reporters heard Turkish fighter jets near the border on Wednesday, shortly after a Syrian warplane bombed Ras al-Ain, sending more Syrian refugees trickling through the barbed-wire fence that divides the town from Turkey.