No longer safe from conflict in the very place they'd sought refuge, an estimated 130,000 Syrian Kurds have crossed into Turkey since Friday, according to the UN Refugee Agency, leading Turkish authorities to lock down some sections of its border. The UN says hundreds of thousands more refugees could follow in the coming days.

The unprecedented number of refugees—many of them women, children, and the elderly—are fleeing Kobani, a predominantly Kurdish border town that came under attack last week by the Islamic State of Iraq and Syria, or ISIS, which has been advancing though the region. Reuters reports that "residents fleeing Kobani said the militants were executing people of all ages in villages they seized."

The current attack is the third push against the strategic border town since June, and comes as ISIS has stepped up its rhetoric against the Kurds, whose secular ideology the militant group denounces.

"Throughout the Syria conflict, the city of Kobani was relatively safe and untouched, and as many as 200,000 internally displaced people from other parts of the country had found refuge there," the UN Refugee Agency said. "But with recent ISIS advances and a siege of the city, large numbers of the population, mainly from Syria's Kurdish minority, were forced to abandon their homes and seek protection and safety in Turkey's Sanliurfa province."

Turkey already hosts at least 850,000 Syrian refugees, with some estimates as high as 1.5 million, and is strained to accommodate more.

"The official borders with Turkey are closed by the Turkish authorities," Redur Xelil, a spokesman for the People’s Protection Units, one of the Kurdish groups fighting the Islamic State, told the Washington Post. "However, the refugees are crossing through wire fences in some areas."

On Monday, the Guardian reported that while "fierce clashes" were still under way to the west and south of Kobani, Syrian Kurdish fighters appeared to have halted the advance by ISIS on the eastern front—aided by Turkish Kurds who crossed the border to aid in the fighting. 

In fact, the Associated Press reports that "the situation has raised tensions between Turkish authorities and Kurds, who claim the government is hampering their efforts to help their brethren in Syria by refusing to let Turkish Kurds cross into Syria."

Skirmishes erupted on Monday along the border near the town of Suruc, with Turkish police firing tear gas and water cannons to disperse Kurds protesting the government or demanding to reach Syria, according to news reports.

Over three million Syrians have fled their homes since the country's civil war began three years ago; the UN Refugee Agency calls the situation "the biggest humanitarian emergency of our time."