Speaking to Aljazeera from Baghdad on Saturday, Iraqi journalist Ziyad al-Samarrai said a fierce firefight broke out just before midnight and continued until early morning.
"In Baghdad's Haifa Street, a gun battle had erupted where about 40 US military vehicles and 200 soldiers were deployed, closing all roads," he said.
"The area near Baghdad's international airport also came under fire when explosions rocked the area on Saturday morning."
A US military statement said on Saturday: "One Task Force Baghdad soldier was killed and another injured by an improvised explosive device at approximately 3.45pm (1245 GMT) on 1 January, north of the Iraqi capital."
The death brings US losses since last year's invasion to 1326, based on a Pentagon tally.
In the Abu Ghraib district near Baghdad, a US tank was damaged when it was hit by an explosive device, planted in an agricultural area. No further details were provided, Aljazeera said.
Separately, in the Iraqi capital's western al-Khadra district police said they had discovered two decapitated bodies in a pair of white bags.
An interior ministry official confirmed the find, and said one of the bodies was that of Muhammad Abd al-Mutallib.
Foreigners and Iraqis working for
US forces have been targeted
Documents were left with his body that showed he worked for US-led forces in Iraq. The second man was not named.
In another incident, in the Diyala province northeast of Baghdad, an unknown group assassinated a leading local Iraqi government official on Saturday, shooting him dead and wounding his brother near the town of Baquba, police said.
Nawfal Abd al-Husain al-Shimari, head of the council governing Diyala province, was killed in a shop. Ali Haddawi, a member of the same council, was shot dead in the nearby town of Khalis, police added.
The provincial capital, Baquba, 65km northeast of Baghdad, has been one of the main centres of anti-US violence.
Also on Saturday, according to Iraqi journalist Fadil al-Badrani, thousands of Falluja residents gathered to protest against US policy in the ruined city.
In addition to the huge amount of destruction, al-Badrani said citizens were angry about difficulties in entering the city.
Falluja residents are shocked by
the damage inflicted on the city
"According to the protesters, dozens of houses were destroyed or burned by US forces after the citizens had returned to the city," al-Badrani said.
"A citizen said he found his house partially damaged when he returned to the city. However, US forces completely destroyed it, along with many other houses, during the last four days."
Many Fallujans also complained of constantly having to face US forces pointing their weapons at them, al-Badrani said.
He said the crowds were demanding that US forces withdraw immediately, allow media teams into the city to document the destruction, compensate citizens for the loss of their homes, and help in reconstruction of the city.
Others expressed health concerns, particularly over decaying corpses and polluted water.
Stringent security measures are
not endearing US troops to locals
Elsewhere, US helicopters bombed an area near a US military base north of Tikrit city, after the base had come under mortar fire.
The US army said in a statement that it had launched a new attack on southern Baghdad, including the Iskandariya, Mahmudiya, Latifiya and Yusufiya areas.
One fighter has so far been killed and nine others arrested during this operation, the statement added.
In another statement, the military said a marine was killed in Iraq's western province of Anbar late on Friday