A suicide bomber detonated an explosive vest in the middle of a Shi'ite Muslim gathering in Baghdad, killing at least 31 people and wounding more than 30 on Saturday, police said. The explosion went off inside a tent filled with people taking part in Shi'ite Ashura rituals, mourning the killing of Prophet Mohammed's grandson Hussein in the 7th century. Some people were also there to mourn the death of a local resident, said authorities.No-one claimed the attack, though so-called Islamic State (IS) have carried out similar attacks in the past. Reports say a militant detonated a suicide vest in the tent at lunchtime, when it was full of pilgrims. The latest attack comes as Iraqi forces prepare for an offensive in northern Iraq on Mosul, the last IS-held major city in the country.