A roadside bomb hit a U.S. military convoy on a highway leading to the capital's airport Friday, setting fire to a Humvee police said.
No casualties were immediately reported, but Associated Press Television News footage from the scene showed the Humvee, its hood open, consumed by flames that sent black smoke up into the air.
Heavily armed U.S. soldiers closed off the area in Khadra, a western neighborhood of Baghdad.
Another explosion was heard in the area a few hours later, but the cause of the blast was not immediately known.
Meanwhile, in Ghazaliyah, a nearby part of western Baghdad, suspected insurgents opened fire on Iraqi soldiers who were conducting a search in the area, said police Maj. Abdul Karim.
After about 30 minutes of fighting, the soldiers withdrew, he said. No casualties were immediately reported.