The US military said three or four explosions rocked Baghdad tonight but there was no immediate word on casualties in the blasts which witnesses said were in the area of the US headquarters in the city.
"I can confirm there were three or four explosions but there are no other details," said a US army spokeswoman told reporters by telephone.
Immediately after the explosions around midnight (local time) sirens could be heard coming from the direction of the US headquarters on the west bank of the Tigris river and helicopters buzzed over the area.
The compound is a sprawling complex of palaces and parkland which the US authorities in Baghdad have turned into a heavily defended fortress.
Earlier today, a suicide car bomb attack at a US military base in Iraq killed one US soldier and wounded 14. US military officials said the bomb was concealed in a furniture truck and detonated outside a base of the US 82nd Airborne Division near the flashpoint town of Ramadi, west of the Iraqi capital Baghdad.
They said the vehicle was driven by a suicide bomber and that there were believed to have been two other Iraqis in the truck who also died in the explosion.
At least 196 US troops have been killed in action in Iraq since Washington declared major combat over on May 1st.