Huge plumes of smoke were seen rising from Kobane as its outnumbered defenders came under intense fire from jihadists who have advanced to its gates despite US-led air strikes against the militants.

At least 60 mortar rounds fired by the Islamic State (IS) group rained down on the Kurdish town Friday, according to the Syrian Observatory for Human Rights, which described it as the heaviest bombardment since mid-September.

It said a Chechen member of the IS organisation was leading the assault on the town, which is considered a strategic prize.

The fierce fighting came a day after the Turkish government won authorisation from parliament to take military action in Syria and Iraq against the jihadists, who include thousands of foreigners in their ranks.

"We will do whatever we can so that Kobane does not fall," Turkish Prime Minister Ahmet Davutoglu said, adding that about 186,000 people had flooded across the border from Syria in less than two weeks.

Damascus was quick to hit back, saying the Turkish stance "represents a real aggression against a member state of the United Nations."

Ankara has not said what action it might take to prevent IS fighters from taking the town, and with it unbroken control of a long stretch of Turkey's more than 900 kilometre (560 mile) border with Syria.

The United States has been working to build a broad international alliance against the jihadists who have declared an Islamic "caliphate" straddling swathes of Iraq and Syria where they have committed widespread atrocities.

The Pentagon said aircraft from Saudi Arabia and the United Arab Emirates joined US warplanes in new bombing raids Friday against IS in Syria.

Coalition planes hit militant tanks, oil refineries and a training camp, it said.

American aircraft also conducted three air raids in Iraq, including two northeast of Fallujah.

- 'Vile crimes' -

Saudi Arabia's top cleric urged Muslim leaders to strike the enemies of Islam with "an iron hand", in an apparent condemnation of the IS group.

Grand Mufti Sheikh Abdul Aziz al-Sheikh's comments came after Saudi Arabia and four other Arab nations joined the Washington in aerial bombardment of IS militants in Syria.

"Your religion is threatened. Your security is threatened," he told Muslims from around the world during the annual hajj pilgrimage, according to the official Saudi Press Agency.

"These criminals carry out rapes, bloodshed and looting," he said, adding that "these vile crimes can be considered terrorism" and their perpetrators have nothing to do with Islam.

The US-led air campaign against IS in neighbouring Iraq received a boost on Friday with Australia's decision to join combat sorties in support of Kurdish forces and the beleaguered Iraqi army.

Despite the air strikes, IS fighters captured parts of the town of Heet, one of the last pro-government bastions in Iraq's western Anbar province, police sources said.

Jihadists also blew up a key bridge in Iraq's Salaheddin province as they retreated in the face of an offensive by pro-government forces.

- 'We are alone' -

In Syria, Kurdish militiamen destroyed two IS armoured vehicles southeast of Kobane, killing seven jihadists, according to the Britain-based Observatory, which has a wide range of sources inside the country.

A Syrian Kurdish official said Kurdish fighters had also destroyed an IS tank, but pleaded for more international support.

"For about 16 days we are defending Kobane. We are alone," Idris Nahsen told AFP by telephone.

"We need help from the international community. We need weapons and ammunition," he said.

Turkish officials have cautioned against expecting rapid military steps by them following parliament's authorisation, and it remains uncertain if Turkish armed forces will be used against the militants.

The lack of action has angered and disappointed many in Turkey's own large Kurdish minority who have watched the jihadist onslaught on their fellow Kurds with mounting horror.

The US is pressing Ankara for the use of the Incirlik air base in southern Turkey by US jets launching assaults on IS in Syria.

But it is unclear if Turkey will allow the transit of lethal weaponry and it may restrict the authorisation to humanitarian aid and non-lethal supplies.

Britain was sending two more fighter jets to Cyprus on Friday, raising to eight the number it has deployed to the air campaign in Iraq.

It follows France's decision to raise to nine the number of jets it is committing to the air war in Iraq.

burs/dr/tl