SYRIAN Kurds have battled to defend a key border town from an Islamic State (IS) advance as Kurdish youths from neighbouring Turkey rushed to their aid, heightening the pressure on Ankara to act against the Islamist insurgents.

In Turkey, which is struggling to manage an influx of more than 130,000 Syrian Kurdish refugees since Friday, security forces fired tear gas and water cannon at hundreds of Kurdish protesters who accuse Ankara of favouring IS against the Kurds.

The main Kurdish armed group in northern Syria, the YPG, said its fighters had halted the IS advance east of the predominantly Kurdish town of Kobani but that fierce fighting was continuing.

Hundreds of Kurdish youths gathered on the Turkish side of the border, responding to calls from Kurdish leaders to join the fight against IS fighters who have seized swathes of Iraq and Syria and proclaimed a caliphate.

Residents fleeing Kobani said the militants were executing people of all ages in villages they seized. Kurds are mostly Sunni Muslims but IS views them as apostates because of their secular ideology. It has persecuted and killed Shi'ite Muslims, Christians and members of the ancient Yazidi sect as well as moderate Sunnis who reject its stark version of Islam.

Turkish security forces are now trying to keep Kurds from crossing the frontier to aid their brethren fighting IS.

At the Mursitpinar border crossing, a line of paramilitary police stood guard along a barbed-wire border fence.

"We all want to cross the border. We tried yesterday but they attacked us, and we will try again today," said balaclava-clad Kurdish activist Shirwan, 28.

The advances by the Sunni insurgents just across Turkey's southern border have alarmed Ankara. But so far Turkey has been slow to join calls for a coalition to fight IS, worried in part about links between the Syrian Kurds and Turkey's own Kurdistan Workers' Party (PKK), which waged an armed campaign for Kurdish rights over several decades.

Turkey strongly denies it has given any form of support to the Islamist militants but Western countries say its open borders during Syria's three-year civil war allowed IS and other radical groups to grow in power.

The PKK has called Turkey's Kurds to arms, saying "supporting this heroic resistance" in Kobani was a "debt of honour".

Deputy Prime Minister Numan Kurtulmus said more than 130,000 Syrian Kurds had fled to Turkey since Friday.

Fierce clashes in Syria continued yesterday but the IS advance to the east of Kobani, scene of the fiercest fighting since the insurgents launched their offensive last Tuesday, had been halted, Redur Xelil, a spokesman for the YPG, said.

He said hundreds of Turkish Kurds were already helping in the struggle to push back the insurgents.

The US has carried out airstrikes against IS fighters in Iraq and says it is prepared to extend them into Syria, but has not said when or where strikes would begin.

Nato member Turkey has so far made it clear it does not want to take a frontline military role. Turkey launched a peace process in 2012 to end a 30-year-old conflict with the PKK which it regards as a terrorist organisation.