Three separate attacks have killed at least 17 people, including 11 government security forces, and injured 40 in and around Baghdad, according to police and hospital officials.

The largest of Wednesday's attacks was in the turbulent Youssifiyah district south of of the Iraqi capital, 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 upscale 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 of a nearby police station as officers were rushing out to the site of the first attack, killing five and injuring 10, all policemen.

There was no immediate claim of responsibility for the attacks, but they all bore the hallmarks of the armed group Islamic State of Iraq and the Levant (ISIL), whose fighters control about a third of the country after they blitzed across much of the north and west of Iraq this year.

Baghdad is hit by near-daily bombings and shootings that kill hundreds of people each month.

And security forces, despite being deployed at checkpoints and other positions across the city, are consistently unable to prevent attacks.

The violence comes as Iraqi security forces and pro-government fighters battle to push back ISIL.

They are now backed by US-led air strikes targeting IS in both Iraq and neighbouring Syria, while Washington and other governments have also pledged trainers to aid Iraqi forces.

'Breaking Beiji siege'

Elsewhere in northern Iraq, government forces backed with Shia fighters are continuing to meet tough resistance from ISIL, a day after they pushed the armed Sunni group out of the town center, a senior military official reached there by telephone said Wednesday.

The official said reinforcements have reached Beiji, 250 kilometers (155 miles) north of Baghdad told Ascociated Press news agency.

Booby-trapped houses and roadside bombs however were hindering their advance toward the northern and northwestern parts of the town, where Iraq's largest refinery is located.

The official spoke on condition of anonymity because he was not authorized to brief reporters.

Lifting the siege of the refinery, which sits inside a sprawling complex whose capacity of some 320,000 barrels a day accounts for a quarter of Iraq's refining capacity, was likely the next objective in the campaign to rid Beiji of ISIL.

When fully retaken, the strategic town will likely be a base for a future push to take back Saddam Hussein's hometown of Tikrit just to the south, one of the main prizes overrun by the extremists last summer.