As many as 40 Iraqi civilians were killed and many badly wounded in a series of huge blasts at an arms dump on the outskirts of Baghdad on Saturday, an Iraqi medic told Reuters.

US troops blamed unidentified attackers who fired flares into the munitions store. But local people turned their anger on the Americans, shooting and forcing them back, soldiers said.

Some soldiers were wounded, an army sergeant-major told Reuters at Zaafaraniya, a mixed residential and industrial suburb on the southern edge of the capital.

Earlier, Reuters photographer Yannis Behrakis had seen furious local people throw stones at American troops.

A series of loud explosions, lasting about an hour, were heard in the city centre from about 8 am [0400 GMT]. US troops said they were caused by controlled detonations to destroy Iraqi munitions as part of a continuing programme.

But later at the scene, an officer told Reuters that assailants had sparked the chain reaction by firing flares into the dump.

A local medic travelling in an Iraqi civilian ambulance ferrying casualties between the blast scene and a hospital said there had been many victims.

Asked how many were killed, he replied: "Forty."

Local people said several people were believed to be still trapped in the rubble of a wrecked building, apparently hit by an errant surface-to-surface missile from the arms storage dump.

An enraged man at the scene vented his fury at the US forces who took the capital two weeks ago: "Why, why?...The war is finished. A baby, a woman, 14 under this building," he screamed in English.

"May God exact his revenge," added a woman, whose head was bandaged. She was seated next to a young girl whose dress was soaked in blood from a head injury. The girl's leg was being bandaged by a soldier.

Whatever the precise cause, the incident seemed likely to hamper US efforts to win Iraqis' support for their presence, however pleased most people are to be rid of Saddam Hussein.