No US troops were hurt in the incident, a US military spokesman said.
Further details on the incident are still unavailable.
Earlier in the day, the military said that a sniper shot dead a US soldier guarding the national museum in Baghdad overnight.
Another 19 were wounded when they came under fire near the town of Balad, north of the capital.
Another soldier was wounded on Friday by a blast targeting a Humvee vehicle on the outskirts of Baghdad, witnesses said.
The blast occurred at 8:30 am (0430 GMT), damaging the Humvee and an Iraqi civilian car.
The soldier appeared to be lightly wounded, according to the witnesses.
US troops also came under fire in the town of al-Ramadi, west of Baghdad, local residents said early Friday, but there was no word on casualties.
Two loud explosions were heard in the area of the former intelligence services base around three kilometers outside Ramadi where US troops are stationed, witnesses said.
Residents of the town of Fallujah, further down on the highway leading to Baghdad, also reported US troops had fanned across the streets in a state of alert after the Ramadi attacks.
At least 10 US soldiers were wounded and three Iraqis killed in four incidents in Iraq on Thursday, a day after US President George W Bush defiantly vowed that resistance attacks would not drive out American troops.
Resistance fighters have stepped up military operations in recent weeks. Attacks launched against occupation forces have become a daily occurrence.
These operations continue despite a large-scale military search-and-destroy operation by US occupation forces in areas to the northeast and north of Baghdad.
Growing Iraqi resistance has made Indian politicians more reluctant to send troops to Iraq as requested by the United States.
"We are now given to understand that our government has not made up its mind and is looking around because it is just not keen on sending troops to Iraq," a highly placed source from Defence Minister George Fernandes' Samata Party said.
"Fernandes too is not particularly keen and it seems the
government is marking time because of the lack of a national
consensus on sending troops," the party source told AFP.
Meanwhile, Japan’s Lower House of parliament passed a bill allowing a troop deployment in Iraq on Friday.
The bill paves the way for Prime Minister Junichiro Koizumi to send about 1,000 troops to Iraq in the near future.
Later this month, the parliament’s Upper House is expected to endorse the bill.
Politicians opposed to a Japanese troop deployment in Iraq include high-ranking ruling party officials.
They say the bill would violate the 1947 constitution which prohibits the use of force to settle international conflicts.
But Koizumi and his cabinet ministers have said the soldiers would be sent to areas “free of military conflict”.
In addition, the UN Security Council unaminously approved a resolution to phase out the “peacekeeping” forces stationed along the Iraqi-Kuwaiti border.
UN Iraq-Kuwait Observation Mission (UNIKOM) has until 6 October to withdraw its remaining operations.
UNIKOM was set up 12 years ago.
As preparations to deal with the Iraqi situation continue, people in the war-torn country are growing more resentful of decisions made by the US occupation administration.
Residents of Najaf expressed their dismay over the US appointment of the mainly Shia city’s governor, Haidar Mahdi Mattar al-Mayali.
“They had to post his picture and his name for us to know who our governor is,” said Ali Hussein, an unemployed teacher.
“This is typical of the state of the country. Just like his predecessor who has been arrested, al-Mayali was appointed by the Americans, he was not elected by us,” he complained.
Al-Mayali replaced his predecessor, Abu Haidar Abd al-Munim, who was arrested last week on charges of kidnapping and theft.