A UN envoy warned thousands could be massacred in the Syrian border town of Kobane if Islamic State jihadists capture it from Kurdish fighters.
Outgunned Kurdish militia were struggling to prevent the jihadists closing off the last escape route for civilians still in the area, prompting an appeal Friday for urgent military assistance.
US-led warplanes have intensified air strikes against IS, which has been attacking Kobane for three weeks, but the Pentagon has said that there are limits to what can be done without troops on the ground.
Washington also warned that the military campaign could lead to reprisal attacks "against US, Western and coalition partner interests throughout the world".
The jihadists' advance has brought the front line to just 1.3 kilometres (little more than three-quarters of a mile) from the Turkish border but Ankara has so far refrained from any action against the jihadists.
Four straight nights of protests among Turkey's large Kurdish minority have left 31 people dead as anger flared over the government's lack of action to save Kobane.
IS now controls 40 percent of the town, according to the Britain-based Syrian Observatory for Human Rights.
As fighting raged, an IS suicide bomber struck to the west of the Kurdish headquarters in Kobane killing two people, and 10 Kurds were killed in an IS ambush on the south side of town, the Observatory said.
US planes conducted nine new airstrikes in Syria on Thursday and Friday, the US military said.
An AFP correspondent on the Turkish side of the border saw a cloud of white smoke rising above Kobane after coalition strikes Friday.