A car bomb near Husseiniyah Ali Basha, a Shia religious hall used for prayers and other religious ceremonies in Baghdad, the Iraqi capital, has left at least 15 people dead and 32 wounded, security and medical officials have said.
No group immediately claimed responsibility for Friday's attack, but Sunni fighters linked to al-Qaeda often target the country's majority Shia population.
The blast was the latest of several targeting Shias in recent days, with more than 159 people killed already in July in attacks that have mostly struck against the denomination.
Elsewhere on Friday, bombs primarily targeting town squares killed eight people.
In Samarra, a predominantly Sunni town north of Baghdad, a suicide bomber detonated a car bomb near Al-Haq square, a focal point for anti-government protesters for months.
The attack took place just before midday prayers near the Al-Razzaq mosque, killing seven people and wounding nine others, police and medics said.
In the mostly Shia town of Kut, south of Baghdad, a bomb set off in Al-Amil square killed one person and wounded 17 others.
Iraq has seen a surge in violence since the start of the year, with the UN reporting more than 2,500 people killed from April through to June, the highest such level since 2008.