Several loud explosions rang out in Baghdad tonight, rattling windows in the centre of the Iraqi capital, witnesses reported.
The US military had no immediate information on the cause of the blasts.
Earlier, a large explosion hit a Baghdad street near the headquarters of the US-led administration, but US soldiers on the scene said there had been no casualties.
The soldiers were investigating to see whether the blast was caused by a bomb or a mortar or rocket attack. Damage was minimal apart from a small crater in the pavement.
Several times this month, guerrillas have fired mortars or rockets at the headquarters of the US-led administration in Baghdad. In response, the US Army has launched "Operation Iron Hammer", a series of air and ground strikes against suspected guerrilla hideouts.