Twelve others were injured in the blast, one of several, on Saturday.
The Ijbala Shia mosque and nearby houses were severely damaged in the attack, an Iraqi journalist, Walid Khalid, told Aljazeera.
Elsewhere in Iraq, a car bomb targeting Iraqi police officers killed four Iraqis, including two children, a police officer and a civilian. Eleven others, including seven police officers, were wounded in the attack in Dora, in southern Baghdad.
In the al-Mashada area, north of Baghdad, an armed group ambushed a 10-vehicle convoy of Interior Ministry police officers, known at the al-Dhib Brigades. The police exchanged fire with the attackers. An unknown number of police were killed and injured, reported Khalid.
British troops dead
Three British soldiers were killed when a roadside bomb exploded in the southern town of al-Amarah, a stronghold of Shia cleric Muqtada al-Sadr, who led an uprising against the US-led forces last year.
Two other British soldiers were wounded in the explosion in the town's Hayae al-Risala district, the Defence Ministry said in London.
UK troops died in a roadside bomb
The deaths brought British losses in Iraq since the 2003 invasion to 92, including accidents and natural causes as well as deaths in action.
Also on Saturday, two US soldiers and three Iraqi troops were injured in a blast caused while they were trying to defuse an explosive device in the al-Dabas district, western Kirkuk.
A second Baghdad bomber blew up a car in an attack targeting a passing US military convoy. One civilian was killed, the Interior Ministry said. There was no immediate word on any US casualties.
A third bomber blew himself up in a police station in Iraq's main northern city of Mosul, killing four police officers and wounding 18 more, police General Wathiq Muhammad said.
Just south of the capital, a fourth bomber blew himself up in the Jabala area, when Iraqi police tried to arrest him. The explosion wounded two police officers and four civilians, police said.