US-led air strikes in Syria are reported to have killed more than 500 jihadists in a month, as fighting raged in the embattled border town of Kobane.

An AFP correspondent across the frontier in Turkey reported fierce clashes in several parts of Kobane early on Thursday, with heavy gun and mortar fire.

The town’s Kurdish defenders have been holding out against an assault by the Islamic State militant group for more than a month, buoyed in recent days by a promise of Iraqi Kurd reinforcements and US air drops of weapons.

Fighter jets were again heard flying over Kobane on Thursday, the AFP reporter said, a month after the US-led coalition expanded its aerial campaign against ISIL in Iraq to Syria.

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The air strikes have killed 553 people since their launch, the Syrian Observatory for Human Rights said, including 464 ISIL fighters and 57 militants from Al-Qaeda affiliate al-Nusra Front.

Thirty-two civilians have also been killed, including six children and five women, said the Britain-based Observatory, which relies on a wide network of sources inside Syria.

Observatory director Rami Abdel Rahman told AFP that the “vast majority” of jihadists killed in the strikes were not Syrians but foreign fighters who had joined ISIL and Nusra in the country.

After first focusing on Iraq, the coalition has dramatically expanded its strikes in Syria in recent days, including at Kobane which has become a crucial battleground in the fight against ISIL.

The jihadist group launched an offensive against the town last month, as it seeks to expand its control over large parts of Syria and Iraq where ISIL declared an Islamic “caliphate” earlier this year.

After initially losing ground, the Kobane Kurds have fought back hard, with the US military saying they had halted the ISIL advance and held most of the town.

But local officials say the exhausted fighters are in desperate need of relief and anxious for promised reinforcements from Iraq’s autonomous Kurdish region.

Iraqi Kurdish MPs in their capital Arbil agreed on Wednesday to send their peshmerga fighters, after Turkey this week said it would allow them to travel to Kobane.

Mustafa Qader, responsible for the peshmerga, said a decision would be made in the coming days about how many to send.

He did not say when the forces would arrive in Syria, but added that “they will remain there until they are no longer needed”.

In Iraq, ISIL fighters had again surrounded Mount Sinjar in the country’s north where they had trapped thousands of civilians this summer, commanders in the area said.

The civilians, mostly members of the Yazidi religious minority, eventually escaped via Syria with the help of Kurdish fighters from Iraq’s neighbour to the west, but that route has now been cut.

“The mountain is besieged” again, and ISIL militants are “trying to climb the mountain on foot to fight the Yazidi volunteers,” Dawud Jundi, a commander of the forces defending the area, told AFP by telephone.

The ISIL push began Monday, when some 300 of the militants with armoured vehicles attacked and seized nearby villages and then turned their attention on the mountain itself.

“We don’t have anything but light weapons,” Jundi said.

On Mount Sinjar, “there are almost 2,000 families whose situations are very bad”, he said.

The first siege of Mount Sinjar was a key moment in the conflict with ISIL, with the plight of the people trapped on the mountain helping to prompt Washington to begin air strikes against the jihadists.

The Iraqi capital Baghdad has also seen a wave of bomb attacks against Shi’ite targets in recent days, with ISIL claiming responsibility for some.

At least 28 people were killed on Wednesday when car bombs went off near a maternity hospital and a service station in areas of the capital where Shi’ites have frequently been targeted.

-AAP