Islamic State militants closed in on Syria's third-largest Kurdish town on Sunday as tens of thousands fled in terror across the border into Turkey.
The UN refugee agency said as many as 70,000 Syrian Kurds had poured into Turkey since Friday, and solidarity protests by Turkish Kurds on the border prompted clashes with security forces.
Syrian Kurdish fighters backed by reinforcements from Turkey are battling to hold off a jihadist advance on the strategic border town of Ain al-Arab, known as Kobane by the Kurds.
The IS group has seized large parts of Iraq and Syria, declaring a "caliphate", imposing its harsh interpretation of Islamic law and committing widespread atrocities including beheadings and crucifixions.
Local officials have warned of potential massacres should IS extremists advance on Ain al-Arab and pleaded for an international intervention.
But despite promises by Washington to expand its air campaign against IS in Iraq to Syria, there were no signs yet of US strikes in the country.
UNHCR said it feared the massive influx of refugees would only grow and said authorities were preparing for the possibility of hundreds of thousands of additional arrivals.
'Waiting for a miracle'
IS fighters have been advancing on Ain al-Arab since late Tuesday, hoping to cement their control over a large part of Syria's border with Turkey.
On Sunday, they were within some 10 kilometres (six miles) of the town, after capturing more than 60 villages in the area, the Britain-based Syrian Observatory for Human Rights group said.
The fighting has killed at least 27 Kurdish militants and 39 IS jihadists, and Kurdish fighters from Turkey have crossed into Syria to join the fray.
There were tense scenes at the border on Sunday after Turkish security forces used tear gas and water cannons to disperse a solidarity protest by Turkish Kurds.
After the clashes, security forces closed most of the border crossing points in the area, including one used by Kurdish fighters heading to Syria.
Only two posts remain open, and the interior ministry will now register new arrivals.
Mustefa Ebdi, a Kobane resident, local journalist and activist, said the streets of the town -- once home to about 50,000 people -- were virtually empty.
"Most of the women and children have left Kobane, but there are thousands of Kurdish men who have taken up arms and are ready to defend the city," he told AFP by telephone, adding that the fighters would have a hard time matching the heavy weapons of IS.
"We need one US airplane to strike those barbarians, where is this is international coalition?" he said. "We are waiting for a miracle."
The Syrian opposition National Coalition has urged foreign air strikes to "stop mass atrocities" if IS advances into Ain al-Arab.
Washington has assembled a coalition of more than 40 countries to fight IS, and has already carried out 183 air strikes against the jihadist group in Iraq.
It has expressed willingness to target the group in Syria, despite warnings from Damascus against violating its airspace.
In Iraq on Sunday, government forces launched an operation to rescue an army battalion that has come under repeated attack by militants near the western city of Fallujah.
"Forces from the interior and defence ministries, counter-terrorism forces and volunteers are advancing to clear the Al-Sijr area," Iraqi military spokesman Qassem Atta told AFP, adding that the operation was backed by US air support.
No 'bargain' for Turkish hostages
International outrage has grown over the group's atrocities including the on-camera beheadings of two US journalists and a British aid worker.
The wife of a British taxi driver being held hostage by the jihadists released a statement on Saturday urging his captors to free him.
Alan Henning, a 47-year-old father of two, volunteered to drive a humanitarian aid convoy to Syria for a Muslim charity but was captured 10 months ago by IS.
In the statement his wife Barbara Henning urged his captors to "see it in their hearts to release my husband".
"I cannot see how it could assist any state's cause to allow the world to see a man like Alan dying," she said.
Turkish President Recep Tayyip Erdogan said Sunday that dozens of Turkish hostages held by Islamic State militants in Iraq had been freed as a result of negotiations and no ransom had been paid for their release.
Forty-six Turks abducted by IS militants in the northern Iraqi city of Mosul were freed and returned to Turkey on Saturday after more than three months in captivity.
"A bargain for money is totally out of the question. There were only diplomatic and political negotiations. And this is a diplomatic victory," Erdogan told reporters at Ankara's Esenboga Airport before departing for New York for a UN General Assembly meeting.