Kurdish fighters backed by US-led air strikes have been locked in fierce fighting to prevent a key Syrian border town from falling into the hands of Islamic State group jihadists.

It came as 41 children were reported dead on Wednesday in twin bombings that hit a school in the government-controlled central city of Homs, which has been devastated by the three-year civil war.

Anti-jihadist air strikes and heavy clashes in the besieged town of Ain al-Arab on the Turkish border killed at least 18 people – nine militants and nine Kurdish fighters, monitors said.

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Ambulances ferried wounded fighters for treatment in Turkey amid mortar fire, with some rounds hitting very close to the border, an AFP correspondent on the Turkish side reported.

The twin blasts in Homs farther south hit a neighbourhood inhabited mainly by the Alawite community of Syrian President Bashar al-Assad, which has been frequently targeted by rebels and jihadists.

One attacker carried out both of the bombings, planting a bomb at one location before blowing himself up nearby.

The dead children were among at least 48 people killed.

There was no immediate claim of responsibility.

About 191,000 people have been killed since an uprising against Assad erupted in 2011, escalating into a several-sided war involving pro-government forces, hardline jihadists and more moderate rebels.

Near the Turkish border, Kurdish forces have been on the defensive for more than two weeks in the face of a jihadist assault that sent tens of thousands of refugees streaming across the frontier.

With IS fighters less than three kilometres from the town, the US-led coalition carried out three air strikes in the area on Tuesday and Wednesday, the Pentagon said.

The US-led coalition of Western and Arab allies has been flying missions in Syria since last week against IS, an extremist Sunni group that has seized control of large parts of the country and neighbouring Iraq.

In Baghdad, a suicide car bombing ripped through a busy commercial street, killing at least 14 people, police and medical sources said.

Iraqi Foreign Minister Ibrahim al-Jaafari said any international assistance in the fight against IS should preserve “Iraqi sovereignty”.

The Pentagon has warned there would be no quick and easy end to the fighting, with spokesman Rear Admiral John Kirby saying: “No one should be lulled into a false sense of security by accurate air strikes.”

And Turkish President Recep Tayyip Erdogan said dropping “tons of bombs” on IS would provide only temporary respite.