The Turkish government won parliamentary approval to deploy troops against the Islamic State group as Australia announced on Thursday that it was joining combat sorties against the jihadists in Iraq.

The vote by Turkish MPs came as IS fighters pressed an assault on a Syrian frontier town, whose capture would give the jihadists unbroken control of a long stretch of Turkey's more than 900 kilometre (560 mile) border with Syria.

An AFP correspondent on the frontier saw huge plumes of smoke above the town of Kobane as outnumbered and outgunned Kurdish militia put up a desperate resistance.

Early Friday, the town's defenders destroyed two IS armoured vehicles which had reached less than two kilometres (little more than a mile) from the town, the Syrian Observatory for Human Rights said.

Australia's decision to join the United States and five European countries in flying combat missions over Iraq came as the coalition stepped up its air war against the jihadists there in support of Kurdish forces and the beleaguered federal army.

In Syria, Washington has so far relied on the support of Arab allies in its air campaign against IS which is now in its 11th day.

But Pentagon chief Chuck Hagel said he had talks with France on Thursday about its joining the strikes.

The vote in the Turkish parliament does not commit the government to sending soldiers into Iraq and Syria where IS has captured large areas, declaring an Islamic "caliphate" and committing widespread atrocities.

But the broad mandate approved by MPs allows the deployment of armed forces in both countries, as well as the transit of foreign forces in Turkish territory for operations against IS militants.

Washington, which has been striving to build an international alliance against the jihadists, welcomed the vote by lawmakers in its key NATO ally.

State Department spokeswoman Jen Psaki said there have been numerous high-level discussions with Turkish officials on fighting the IS threat, and that Washington looks "forward to strengthening that cooperation".

The United States 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 may restrict the authorisation to humanitarian aid and non-lethal supplies.

Five Arab nations have supported the US-led strikes on Syrian soil while the same number of European countries have committed aircraft to Iraq.

On Friday, they were joined by Australia, whose Prime Minister Tony Abbott said the cabinet had also authorised the deployment of special forces to advise and assist Iraqi forces alongside British, Canadian and US advisers already on the ground.

The special forces were "not envisaged" to become directly involved in combat missions but would be "helping Iraqi forces with the planning and coordination of operations", Abbott stressed.

Some 1,600 US soldiers have been deployed to support Iraqi forces with equipment, training and information, while Canada said last month it had sent dozens of special forces soldiers to advise Iraqi personnel.

The Australian move came as Iraqi troops remained under heavy pressure from IS in Sunni-dominated Anbar province west of Baghdad and as Kurdish counter-offensives in the north made slow progress despite coalition air support.

Troops of the Shiite-led Baghdad government repulsed jihadist assaults on two of their remaining bases in the province on Wednesday night but with the loss of at least 17 men.

Retired US general John Allen, who is leading the international effort against IS, arrived in Iraq on Thursday for talks on boosting the campaign, the State Department said.

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.

The announcement was made by Prime Minister David Cameron during a visit to Britain's Akrotiri air base on the Mediterranean island.

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

Hagel said that he had raised the possibility of France expanding its flights to Syria in Pentagon talks with his counterpart Jean-Yves Le Drian.

The French minister declined to confirm or deny the issue had been raised.

Fresh US-led raids in Syria on Thursday destroyed an IS checkpoint near the besieged Syrian border town of Kobane and hit two tanks elsewhere, the Pentagon said.

But Syrian Kurdish leaders have pleaded for more extensive coalition air support against the heavy weaponry of IS, large stocks of which it seized from the fleeing troops when it captured Iraq's second city Mosul in June.