Eight other people were killed in attacks elsewhere in Iraq on Monday - five members of a Shia religious party shot dead in Baqouba and three police officers who died in separate incidents in Baghdad and Iskandariyah.
The attack outside the bank occurred in the eastern district of New Baghdad at 9.40am as people lined up to receive government cheques in compensation for food rations that were incomplete in the last few months.
Ali Abbas, a police spokesman, said the attacker joined the line and blew himself up while security guards were searching people before allowing them to enter the bank. The wounded included three children and nine women, he said.
Elsewhere, armed men killed three brothers and two of their sons in an attack on a street in Baqouba, 60km northeast of Baghdad, Diyala police's Joint Co-ordination Centre said.
US and Iraqi soldiers are yet to
restore order in Iraq
All five were identified by police as members of the Supreme Council for the Islamic Revolution in Iraq, the country's leading Shia political party, police said.
A roadside bomb attack in Iskandariyah, 50km south of Baghdad, killed two police officers and wounded another, said Babil police's information office. An Iraqi police officer protecting electricity generating facilities near a hospital in eastern Baghdad's Sadr City was also shot dead, police said.
Also on Monday, Ayham al-Samarie, Iraq's former electricity minister, escaped injury when a roadside bomb exploded near his three-vehicle convoy in Baghdad, but two bodyguards were wounded, said Maitham Abdul-Razzaq, a police spokesman.
The bomb hit the convoy of al-Samarie, a dual Iraqi-US citizen, as it passed through Baghdad's western Mansour district, said Mohammed al-Jibouri, an official at the former minister's office.
Another roadside bomb exploded in Baghdad's southwestern Baiyaa neighbourhood, wounding two Iraqi police officers in a patrol, police said.