Islamic State jihadists met dogged Kurdish resistance Sunday in the high-profile Syrian battleground town of Kobane but in Iraq they put forces under strong pressure, prompting US-led relief drops.

A roadside bomb killed the police chief in Iraq’s Anbar province, between Baghdad and the Syrian border, where Pentagon officials have voiced concern about the government’s vulnerability to a renewed jihadist offensive.

Thick smoke in Kobane’s city centre

Farther north, around the key oil refinery town of Baiji, the Iraqi army and its Sunni Arab tribal allies came under fresh attack by IS, prompting a first resupply operation by coalition aircraft.

In Kobane, a huge pall of black smoke hung over the strategic town as the Syrian Observatory for Human Rights reported the jihadists were taking heavy losses.

IS poured in reinforcements from Syria and later fired at least 11 rocket-propelled grenades into the town centre, said the Britain-based monitoring group.

The Kurds managed to advance 50 metres (yards) towards their headquarters, two days after the jihadists captured it but failed to deliver a knockout blow.

“They are sending fighters without much combat experience,” Observatory director Rami Abdel Rahman said.

“They are attacking on multiple fronts but they keep being repulsed, then countering and being pushed back again.”

IS has earned worldwide infamy for committing atrocities — often videotaped and posted on the Internet — since it seized swathes of Iraq and Syria in lightning offensives earlier this year.

But it has also gained prestige among Islamist extremists that has helped it recruit thousands of foreign fighters, a reputation now on the line in Kobane.

“It’s a decisive battle for them,” said Abdel Rahman.

“If they don’t pull it off, it will damage their image among jihadists around the world.”

– UN warning of ‘massacre’ –

In Cairo, UN chief Ban Ki-moon urged action to prevent a “massacre” in Kobane.

The UN has warned that hundreds of mainly elderly civilians in the centre and thousands more on the outskirts all risk massacre if the jihadists sever the sole escape route to the border.

The US military said Sunday that it and its Saudi and Emirati allies conducted four air strikes in Syria. All but one were in Kobane, where an IS fighting position was among targets destroyed.

Despite such raids, Pentagon officials have said there is a limit to what they can do without forces on the ground they can work with.

But the top US officer said American military advisers were likely to take a more direct role once Iraqi forces are ready to fight to retake the country’s second city Mosul, which IS overran in June.

“My instinct at this point is that will require a different kind of advising and assisting because of the complexity of that fight,” General Martin Dempsey said Sunday.

Washington has said it is deeply concerned about the humanitarian risks of Kobane’s fall but vowed to keep to its overall strategy of prioritising the campaign in Iraq.