Three American were killed in a grenade attack northeast of Baghdad on Saturday, the US Central Command said.

The soldiers, from the 4th Infantry Division, were guarding the Ba'qubah Children's Hospital.

Four soldiers were wounded in the attack and were evacuated to a US medical treatment facility, according to the Central Command.

The attacks bring to 47 the number of US troops killed since President George W Bush declared an end to hostilities on May 1. Fifty-seven have died in what the Pentagon calls 'non-hostile' incidents.

A total 242 US military personnel have been killed since the war began in March.