Islamic State fighters have besieged a Kurdish city in northern Syria after seizing 21 villages in a major assault, prompting a call to arms from Kurds in neighbouring Turkey who urged followers to go and help resist the group's advance.

Thursday’s attack on the city of Ayn al-Arab, known as Kobani in Kurdish, came two days after a top US military officer said the Syrian opposition would probably need the help of the Syrian Kurds to defeat the Islamic State (ISIL) fighters.

ISIL fighters, armed with heavy weaponry including tanks, seized  the villages near Kobani in an offensive which the UK-based Syrian Observatory monitoring group said had started on Tuesday night.

Live Box 2012108933861442

It said 21 villages had fallen to Islamic State in the last 24 hours.

"We've lost touch with many of the residents living in the villages that [ISIL] seized," Ocalan Iso, deputy head of the Kurdish forces in Kobani, told the Reuters news agency via Skype.

He said the group was committing massacres and kidnapping women in the newly-seized areas, giving the names of 28 members of a single family he said had been taken captive. It was not possible to verify his account immediately.

The Kurds were appealing for military aid from other Kurdish groups in the region including the Kurdistan Workers' Party (PKK), he said.

Support from Kurds who crossed from Turkey helped to repel an ISIL attack on Kobani in July. Turkish PKK rebels later issued a call for young men in Turkey's southeast to join the fight in northern Syria.

"The youth of northern Kurdistan [southeast Turkey] should go to Kobani and take part in the historic, honourable resistance," the PKK said in a statement on its website.

Footage posted on YouTube on Wednesday by the YPG, the main Kurdish armed group in Syria, appeared to show Kurdish fighters armed with assault rifles and rocket-propelled grenades battling a tank flying the Islamic State's black flag west of Kobani.

Complex relations

Turkish Prime Minister Ahmet Davutoglu said the governors of border provinces in Turkey, where Kurdish fighters have waged a three-decade insurgency to push for greater autonomy, had been ordered to extend aid to refugees on the Syrian side of the border.

Western states have expanded contact with the main Syrian Kurdish party, the PYD, since the ISIL seized wide areas of Iraq in June. The YPG, which says it has 50,000 fighters, says it should be a natural partner in a coalition the US is trying to assemble to fight the ISIL.

But the Syrian Kurds' relationship with the West is complicated by their ties to the PKK - a group listed as a terrorist organisation in many Western states because of the armed insurgency it waged for Kurdish rights in Turkey.

Source: Reuters