Turkish security forces have used tear gas and water cannon to disperse Kurds who had gathered in support of Kurdish refugees fleeing attacks in Syria, and those battling ISIL fighters on Syrian soil.

Hundreds of young demonstrators fought back on Sunday by hurling rocks and setting up barricades on the road leading to a nearby border crossing, the AFP news agency said. At one point the border was sealed.

The security forces kept demonstrators away from a barbed-wire border fence just 5km from Ain al-Arab, known to the Kurds as Kobane, where Kurdish fighters are battling ISIL.

"We've come to support our brothers in Syria under attack by ISIL," demonstrator Mehmet Eminakma told AFP.

Mehment said that Turkish authorities were preventing young Syrian Kurd refugees from returning to the battlefront.

ISIL fighters have captured dozens of villages along the Syrian borders, threatening the largely-Kurdish inhabitants of the northern Kobane area.

The Kurdistan Workers' Party, or the PKK, renewed its call for arms as Kobane came under fierce attack by ISIL for the fourth day in a row. One Kurdish commander said ISIL was within 15km of Kobane.

"Supporting this heroic resistance is not only a debt of honour for the Kurds, but for all of the Middle East people. Just giving support is not enough. ISIL must drown in the blood it spills. The youth of North Kurdistan must flow in waves to Kobani," the party said in a statement.

Ibrahim Binici, a politician for Turkey's pro-Kurdish HDP, told the Reuters news agency that he had been told by locals that ISIL fighters were beheading people as they went from village to village.

"Rather than a war this is a genocide operation," he said.

Kurdish exodus

About 100,000 Syrian Kurds have crossed the border into Turkey over the past few days, fleeing an advance by ISIL, the UN said on Monday.

The Turkish government "confirmed the figure" of 100,000, said Melissa Fleming, the spokeswoman for the UN refugee agency, the UNHCR.

The UN body on Saturday said that as many as hundreds of thousands of refugees might flee the fighting.

Carol Batchelor, the UNHCR's representative in Turkey, said that the ferocity of the fighting and the fast-moving situation near Kobane made any cross-border aid efforts impossible, meaning there was no option other than to keep the Turkish border open.

"We need to be able to say to the Syrian people, and to the host communities who have been helping them for three-and-a-half years, that they have solidarity and their humanitarian life-saving needs will be met."