GENEVA (Reuters) - The United Nations refugee agency said on Tuesday it was making contingency plans in case all 400,000 inhabitants of the Syrian Kurdish town of Kobani fled into Turkey to escape advancing Islamic State militants.
Some 138,000 Syrian Kurdish refugees have entered southern Turkey in an exodus that began last week, and two border crossing points remain open, the U.N. High Commissioner for Refugees (UNHCR) said.
"We are preparing for the potential of the whole population fleeing into Turkey. Anything could happen and that population of Kobani is 400,000," UNHCR chief spokeswoman Melissa Fleming told a news briefing in Geneva.
"We don't know if all of those people will flee, but we are preparing for that contingency," she said.
The United States and Arab allies bombed Syria for the first time on Tuesday, killing dozens of Islamic State fighters and members of a separate al Qaeda-linked group, pursuing a campaign against militants into a war at the heart of the Middle East.
On Monday, Syrian Kurds battled to defend the key border town of Kobani from an Islamic State advance as Kurdish youths from Turkey rushed to their aid.
A first airlift of supplies for up to 200,000 people is due to arrive at Adana airport from Amman, Jordan on Wednesday, to be followed by three more flights later in the week, Fleming said.
Rupert Colville, U.N. human rights spokesman, told the briefing on Tuesday: "Our biggest worry at the moment would be if Kobani itself, the town, fell."
At least 105 villages around Kobani have been captured by Islamic State forces since Sept. 15, including at least 85 over the weekend, he said. The U.N. rights office had reports that an additional 100 villages had been abandoned or evacuated for fear of being captured, he said.
"We have received very alarming reports of deliberate killing of civilians, including women and children, the abduction of hundreds of Kurds by ISIL, and widespread looting and destruction of infrastructure and private property," he said, using another name for the Sunni militant group.
The Kobani region, which has some 440 villages, is also host to between 200,000 and 400,000 Syrians displaced from other parts of the country including Raqqa, Aleppo and Homs, he said.
"So potentially the population movement could be much greater than it's been already even though it's been very large and very fast," Colville said.
Turkish authorities are checking arriving Syrians to ensure they are not fighters, "to maintain the civilian character of asylum", Fleming said. Young Syrian children are also being checked for measles and polio vaccinations, she said.
Fleming called for support for the government of Turkey and other neighboring countries - Lebanon, Iraq, Jordan and Egypt - that are already hosting more than 3 million Syrian refugees.
"If you want to put it into proportion, this 138,000 that just arrived in Turkey represents about the number that all of Europe has taken in the three years of the Syria war," she said.
Reporting by Stephanie Nebehay; Editing by Sophie Walker