A suicide bomber detonated explosives Monday outside a Shiite mosque in central Baghdad, killing at least 11 people in the second such attack in the capital in 24 hours, officials said.
"It was a suicide attack that targeted people who were just leaving Husseiniyat al-Khayrat" after midday prayers in the Sinak area, a police colonel said.
At least 26 more people were wounded, according to the officer and a medical official.
The attack comes less than a day after a suicide bomber attacked another Shiite mosque in central Baghdad, killing at least 22 people and wounding at least 36.
Baghdad has in recent days seen a rise in the number of bomb attacks, several of which have been claimed by the Islamic State jihadist group.
The spate of bombings has raised fears that the extremist group would seek to attack large gatherings of Shiite worshippers during the month of Muharram, which starts at the end of the week.
The second-holiest month in the Islamic calendar after Ramadan includes the Ashura commemorations, during which hundreds of thousands of Shiite faithful converge on the holy city of Karbala on foot.
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The event has been marred by devastating bombings in past years and on Monday militants signalled they were able to strike the city, which lies about 80 kilometres (50 miles) south of Baghdad.
Four car bombs exploded in the Karbala area, killing at least two people and wounding at least 16.
Police spokesman Colonel Ahmed al-Hasnawi said two car bombs went off about one kilometre east of the old city, which houses the mausoleums of Imam Hussein and his half-brother Abbas, who were both killed in 680 AD in the formative confrontation of Shiite Islam.
Another exploded south of the city, while the fourth targeted a checkpoint to its north.
The faithful who want to march to Karbala from Baghdad have to walk through an area which has been known as the "triangle of death" and where almost daily attacks are carried out.
The procession will pass close to Jurf al-Sakhr, a farmland area southwest of the capital which has been one of the deadliest frontlines in Iraq since the Islamic State group's June offensive, which saw the jihadists seize large areas.
Iraqi government forces, backed by US-led air strikes, have strived to pin back the jihadists there, partly in a bid to secure the area ahead of the Ashura mourning rituals.