Video footage showed a bomber slam a car into heavy defences around the concrete towers of the Palestine and Sheraton hotels, blasting a path for another in a cement truck, who struck five minutes later. In between, a second explosion went off close by.
The cement truck, which appeared to be blocked from reaching the base of one of the hotels, exploded close to a US Bradley armoured vehicle on guard duty, sending flames and dust high in the air across the city centre.
There were no initial reports of US military casualties, a US military spokesman said. Recent media reports have focused attention on the fact that the US death toll in Iraq is just three short of the headline figure of 2,000.
Gunmen killed 12 Iraqi construction workers on Monday in an attack in the town of Mussayyib, south of Baghdad, police said.
Iraqi police found the bodies of six Iraqis, three of them women, bound and blindfolded, with gunshot wounds to their heads and chests, near the volatile town of Latifiya, just south of Baghdad.