Manbij, located in the northern province of Aleppo, is on the Islamic State group’s main supply route between Syria and Turkey

Beirut (AFP)

Islamic State group militants clashed Saturday with US-backed fighters in the Syrian town of Manbij, pursuing their fierce defence of the jihadist stronghold and ignoring a deadline to leave.

There are growing fears for the fate of civilians trapped in Manbij, formerly a key stop along IS’s supply route from neighbouring Turkey into its self-styled Islamic “caliphate” in Syria.

The US-backed Syrian Democratic Forces (SDF) penetrated the town one month ago but have since been hindered by a bloody IS counter-offensive and concerns about the civilian population.

On Saturday, IS jihadists appeared to ignore a 48-hour ultimatum to leave issued by the Manbij Military Council, a key member of the SDF.

“The 48-hour period is over, and there will be no more opportunities like this one for Daesh (IS),” a commander from the council told AFP on condition of anonymity.

IS has “not responded” to the SDF’s offer and had instead “attacked our positions” in the town, he said.

The ultimatum came after at least 56 civilians, including children, were reportedly killed Tuesday in US-led coalition air strikes near Manbij.

The commander pledged that his forces would “intensify our attacks on their remaining positions” there while working to “secure safe passages” for civilians looking to flee.

Thousands of civilians have already fled Manbij, which lies in Syria’s northern Aleppo province.

More than half of Syria’s population has been displaced since the country’s conflict erupted five years ago, and at least 280,000 people have been killed.

– ‘Fight like we haven’t seen’ –

An SDF field commander inside Manbij told AFP that clashes were rocking the flashpoint town on Saturday, with “the main battles near the security quarter in the centre of the town.”

The civilian deaths in Tuesday’s raids sparked an intense backlash from activists and rights groups, as well as a call from a prominent Syrian opposition body for the coalition to halt its air campaign until a thorough investigation is completed.

The coalition has said it is investigating the reports of civilian fatalities in the town of Al-Tukhar, 14 kilometres (nine miles) from Manbij.

Bombing raids have meanwhile continued unabated, with the Pentagon reporting nine strikes near Manbij on Friday.

Coalition spokesman Colonel Chris Garver said on Friday that IS was mounting an exceptionally tough fightback.

The battle has grown more intense as SDF units move deeper in the town, he said, “which is sort of different than what we saw in Ramadi and what we saw in Fallujah,” two Iraqi cities from which jihadists were ousted this year.

“It’s a fight like we haven’t seen before,” said Garver.

He estimated that the SDF had taken back roughly half the town, an area still housing at least 2,000 civilians.

– IS use ‘human shields, bait’ –

IS was using residents of Manbij “as human shields and as bait” in order to draw the fire of the SDF towards civilians, Garver added.

Rami Abdel Rahman, head of the Syrian Observatory for Human Rights, accused IS of “pushing children towards the frontlines” as it tried to defend its positions.

Garver said that Tuesday’s controversial air raid was called after the SDF “observed a large group of Daesh (IS) fighters in a convoy who appeared to be readying for a counterattack.”

“The strike was against both buildings and vehicles,” but the coalition later received reports that there may have been civilians mixed in among IS militants, he added.

Earlier this year, the coalition said 41 civilians had been killed in its bombing raids in both Iraq and Syria since August 2014.

But the Britain-based Observatory says that in Syria, 594 civilians across the country have been killed in coalition raids — more than 100 of them in Manbij alone.

IS and its jihadist rival Al-Nusra Front are not included in global efforts to put an end to fighting in war-ravaged Syria.

Repeated attempts by Washington and steadfast regime ally Moscow to reinforce a nationwide ceasefire have largely failed, with violence continuing across the country.

Dozens of civilians died in bombardment across the country Saturday, the Observatory said, with 10 killed in raids by unidentified warplanes in eastern Deir Ezzor province and eight dead in suspected Russian strikes in Syria’s northwest.

Another seven civilians from a single family, including four children, were killed in raids in central Hama province, and two civilians died in barrel bomb attacks in besieged parts of northern Aleppo city, the monitor added.