Suspected Islamic State (Isis) supporters launched attacks in and around Baghdad yesterday, killing 17 people including 11 soldiers and policemen.

The largest of the attacks was in Youssifiyah district south of Baghdad where a suicide car bomber hit an army checkpoint, killing six soldiers and injuring 16, including 10 civilians and six soldiers.

Earlier in Baghdad’s up-market Mansour district, a car bomb near a cluster of shops killed six civilians and wounded 13.

Minutes later, a suicide bomber blew himself up at the entrance to a nearby police station as officers were rushing out to the site of the first attack, killing five policemen and injuring 10 others.

There was no immediate claim of responsibility for the attacks, but they bore all the hallmarks of Isis, whose fighters control about a third of the country after they blitzed across much of the north and west of Iraq this year.

Elsewhere, Iraqi government forces backed by Shi’ite militiamen continue to meet tough resistance from Isis fighters in the refinery town of Beiji, a day after they pushed militants out of the town centre.

A senior military official said that reinforcements had reached Beiji, 155 miles north of Baghdad, to protect areas of the town now under government control.

Booby-trapped houses and roadside bombs, however, are hindering their advance toward the northern and north-western parts of the town, where Iraq’s largest refinery is located.

Lifting the siege of the refinery is likely to be the next objective in the campaign to rid Beiji of the militants.

The sprawling complex has a capacity of about 320,000 barrels a day, accounting for a quarter of Iraq’s refining capacity.

When fully retaken, the strategic town will probably be a base for a future push to take back Saddam Hussein’s home town of Tikrit, just to the south, which was one of the main prizes overrun by the extremists in summer.

The government advance has been assisted by US-led coalition air strikes against Isis forces in the area around Beiji, which have targeted heavy artillery deployed to harass the army and its Shi’ite militia allies.