At least 17 people have been killed and 80 wounded by explosions that destroyed a mosque in the Iraqi capital Baghdad, medical sources say.
The government said the blasts on Wednesday night were the result of the detonation of an ammunition cache in the Shia Muslim district of Sadr City.
It did not give an exact location of the cache, but some security officials said it was inside the mosque.
The mosque was used by supporters of the Shia cleric Moqtada Sadr.
Mr Sadr led a nationalist alliance that includes a number of mostly secular groups to victory in last month's parliamentary elections, winning 54 out of 328 seats.
He also commands a militia that fought US troops after the 2003 invasion of Iraq but has in recent years been supporting US-backed Iraqi security forces in the battle against the jihadist group Islamic State (IS).
A police source told AFP news agency that the ammunition cache had belonged to an armed group and contained rocket-propelled grenades and shells.
The government said an investigation was under way to determine why the cache exploded, but one report said it was believed to have happened during the transfer of ammunition to a vehicle.
"They put ammunition inside a mosque. The ammunition exploded, destroying houses," Umm Ahmed, a woman who lives nearby, told Reuters news agency.
"We appeal to Moqtada Sadr to follow up this incident. This group destroyed our life. Our properties and houses were levelled to the ground. Our sons and daughters were killed."
On Thursday, Mr Sadr called on his followers to exercise "patience and self-control" and said an investigative committee would report to him within three days.