By Seyhmus Cakan and Tom Perry
SANLIURFA, Turkey/BEIRUT (Reuters) - Kurdish-led militia backed by U.S.-led air strikes fought Islamic State near a Syrian town at the Turkish border on Sunday, a monitoring group and a Kurdish official said, in an advance that has worried Turkey.
Concerned about an expansion of Kurdish sway in Syria, Turkish President Tayyip Erdogan said Kurdish groups were taking over areas evacuated by Arabs and Turkmen, saying that might eventually threaten Turkey's borders.
The Kurdish-led YPG, working with the U.S.-led alliance and small Syrian rebel groups, has pushed into Islamic State's Syrian stronghold of Raqqa province, threatening one of its supply lines to the jihadists' de facto capital, Raqqa city.
While dealing a blow to Islamic State, seizing Tel Abyad would also help the YPG to link up Kurdish-controlled areas of northern Syria. Turkey is worried about the risk of separatist sentiment among its own Kurdish minority in the southwest.
At least 13,000 people have fled into Turkey over the past week to escape the fighting near Tel Abyad.
On Sunday, Turkish authorities reopened the border after a few days of closure, a security source said, adding that they expected as many as 10,000 people to come across.
Local media said Islamic State militants had tried to prevent refugees from crossing into Turkey.
"(Islamic State) doesn’t want people to flee. They are telling them the coalition forces would bomb the town if the civilians left," the security source said.
Islamic State militants had forced refugees who fled the fighting back to the town of Tel Abyad late on Saturday, television footage from the scene showed.
YPG fighters were battling Islamic State militants on the eastern outskirts of the town on Sunday, YPG spokesman Redur Xeili told Reuters. Coordination with the U.S.-led alliance was "excellent" with air strikes conducted according to need.
"The road connecting Tel Abyad and Raqqa city is in our firing range," he said.
The Syrian Observatory for Human Rights, which tracks the conflict, said there were only around 150 Islamic State fighters in Tel Abyad.
An activist group, Raqqa is Being Slaughtered Silently, said on its Twitter feed that Islamic State had stripped a Tel Abyad hospital of all its equipment and had moved it to Raqqa city. It also said fighters were ordering people away from the border area.
ERDOGAN SEES POSSIBLE BORDER THREAT
The YPG has emerged as the main partner on the ground in Syria for the U.S.-led alliance that has been bombing Islamic State in Syria and Iraq. Its advance into Raqqa province follows a campaign that drove Islamic State from wide areas of neighboring Hasaka province.
Turkey views the YPG as part of the PKK, which has fought a decades-long insurgency against Ankara and is considered a terrorist organization by Turkey, the United States and the European Union.
Erdogan, in comments published on Sunday, reiterated his view that Arabs and Turkmen were being targeted by the advance.
Kurdish groups were "being placed into regions that they are evacuating. This is not a good sign. Because it means paving the way for a structure which could threaten our border", he said.
Rami Abdulrahman, who runs the Observatory, said the people who had fled into Turkey were escaping fighting and there was no systematic effort to force people out.
He said also said there were no Turkmen in the area: "There are violations by individuals from the YPG, but not in a systematic way."
(Additional reporting by Humeyra Pamuk in Istanbul and Naline Malla in Beirut; Writing by Tom Perry; Editing by Robin Pomeroy and Digby Lidstone)