A suicide bombing targeting Shia Muslims killed at least four people in Baghdad on Sunday, officials said, a day after the deadliest attack to hit the Iraqi capital in months.

The bombing in central Baghdad, which targeted a tent where Shias distribute food as part of annual religious commemorations, also wounded at least 12 people, officials said.

There was no immediate claim of responsibility for the attack, but the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group frequently carries out suicide bombings targeting Shias, whom it considers heretics.

The blast came a day after an ISIL-claimed suicide bombing at a funeral killed at least 34 people - the deadliest attack in Baghdad since another ISIL suicide bombing left more than 300 dead in early July.

The attacks come as Iraqi forces prepare for an offensive in northern Iraq to retake Mosul, the last ISIL-held city in the country, after regaining much of the territory the fighters seized in 2014 and 2015.

Battle for Mosul

The launch of the operation is expected to be announced soon, but it will mark only the start of a battle that is likely to be the most difficult and complex yet in the war against ISIL.

Iraqi aircraft dropped "tens of thousands" of leaflets, some bearing safety instructions for Mosul residents, ahead of the operation, the military said.

Iraq has dropped leaflets over Mosul before, and has also done so as part of operations to retake other cities seized by ISIL in 2014 and 2015.

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Aircraft dropped "tens of thousands of newspapers and magazines on the centre of the city of Mosul carrying important news... to inform them of updates and facts and victories," said Iraq's Joint Operations Command, which distributed images of some of the leaflets.

One image showed a leaflet containing safety instructions for Mosul residents, urging them to tape over windows to prevent the glass from shattering, to avoid the sites of air strikes for at least an hour after a place is bombed, and saying they should not drive if possible.

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Source: Agencies