Dr Ali Muhammad of Talib al-Janabi hospital said the men were killed when US forces, trying to capture parts of Falluja on Sunday, opened fire in the east of the town.
Earlier, witnesses and doctors said US forces had killed four others in an air strike late on Saturday.
US forces have launched frequent air strikes in and around Falluja against targets they say are linked to Abu Musab al-Zarqawi, an alleged al-Qaida ally.
The US military said in a statement it had carried out a "precision strike" late on Saturday against a fighters' checkpoint linked to al-Zarqawi on the northern outskirts of Falluja, west of Baghdad.
The military said the checkpoint was used to interrogate and detain locals. "Informants linked the checkpoint to kidnappings and executions in the Falluja area," the statement said.
Meanwhile, in Baghdad, two Iraqis were killed in an explosion on the main highway in al-Amil neighbourhood west of the capital, sources told Aljazeera on Sunday.
The victims were inside a car that was totally burnt, they added. After the explosion, Iraqi police and a US tank were deployed at the site.
Iraqis help a man in shock after
the death of a relative in Falluja
In a separate development, a car bomb near Samarra north of Baghdad killed an Iraqi soldier and wounded three US troops, the US military said.
Another three Iraqi soldiers were wounded when fighters
exploded a car bomb as a joint US-Iraqi patrol approached a
four-door sedan at around 1100 GMT.
The wounded soldiers were all evacuated to a US medical centre.