A car bomb has torn through a cafe packed with young men watching a football match in a predominantly Shia area of southern Baghdad, the Iraqi capital, killing at least 16 people.
It was the first major attack in Iraq since US commandos killed Osama bin Laden, the al-Qaeda leader, in Pakistan.
The explosion occurred in Abudsheer, a Shia enclave in the former al-Qaeda stronghold of Dora, an area of the capital which saw some of the fiercest fighting of the Iraq conflict.
"It was a bomb inside a vehicle which resulted in the death and injury of a number of civilians in the district of Abudsheer," said Major-General Qassim al-Moussawi, Baghdad's security spokesman.
Al-Qaeda operatives have vowed revenge for bin Laden's death on Sunday. Nobody has claimed responsibility for the attack.
Most of the dead and wounded were young people watching a football match, said police and hospital officials.
A vendor selling food near the cafe also was among the dead. Many locals were quick to blame al-Qaeda for the attack.
"This is the cowardly reaction of al-Qaeda after the killing of the big terrorist bin Laden. They intend to do this against such gatherings in Shiite areas," Jasim Hashim, a 20-year-old student who lives about 200 metres from the scene of the explosion.
He said his parents had refused to let him go out, fearing just such an attack after bin Laden's capture, but one of his close friends was at the cafe and killed in the attack.
Iraqi security forces have been on high alert since the killing of bin Laden.
Security officials said they expected the organisation's local affiliate to carry out revenge attacks.
Violence has fallen sharply in Iraq in recent years from the peak of sectarian violence in 2006-07 but fighters still launch dozens of bombings and other attacks each month.
The head of Iraq's grain board was wounded in an apparent assassination attempt on Tuesday when a roadside bomb hit his motorcade in Baghdad.
Hassan Ibrahim suffered fractures and other wounds in a blast that killed his driver.
He was appointed in March to lead the body that provides Iraq, one of the world's largest grain importers, with wheat and rice for its national food ration programme.