An Iraqi armed group later claimed responsbility for bringing down the helicopter on Saturday.
"The lions of Islam in the Maath bin Jabal brigade of Al-Rashideen Army managed to down a helicopter of the US occupation forces in the Yussifiyah area south of Baghdad," said the statement, whose authenticity could not be confirmed.
In northeast Baghdad, six Shia men were killed by armed men when their minibus was attacked northeast of Baghdad, Iraqi officials said, adding to a day when a further 19 people lost their lives, many of them to drive-by shootings.
The Shia men were returning from a visit to relatives when they were ambushed on Friday night near the town of Balad Ruz, about 70km from the capital Baghdad, according to the town's mayor.
The motive for the attack remains unclear. However, the area has Shia and Sunni residents and has witnessed numerous sectarian acts of violence.
Also, armed men killed three ice cream vendors in the capital's southern neighbourhood of Dora and a butcher and his son in east Baghad, police said. Another son was also wounded in the attack on the butcher shop.
There has been no let-up in
violence in Iraq
In the western Iskan neighbourhood, assailants killed the owner of an air-conditioner repair shop on his way to work.
A Sunni sheikh was killed by armed men in a speeding car when he left his home in the southern city of Basra. His brother, who was with him, was wounded, a Sunni official said.
Police reported the discovery of at least eight bodies, mostly young men who were shot in the head or strangled in Baghdad.
Witnesses also told police they saw three armed men in a BMW pull a handcuffed man out of the car and shoot him near a highway in west Baghdad.
West of Baghdad, US and Iraqi troops killed three suspected fighters, including a woman, and captured three others on Saturday in an operation in Amiriyah in Anbar province, the US military said.
South of Baquba, an Iraqi army sergeant major was killed on Friday after his patrol surprised a group of suspected anti-government fighters trying to steal a dump truck.