A US helicopter killed two civilians and injured four more while opening fire on gunmen attempting to plant an explosive device in central Samarra city, independent Voices of Iraq news (VOI) agency quoted an Iraqi police source as saying Monday, according to DPA. Three gunmen were killed Sunday in the raid, the source added. The US military did not comment immediately on the incident. Samarra, a city in Salahaddin province, lies 120 kilometres north of Baghdad. Meanwhile, at least two people were killed and four wounded Monday when a car bomb exploded near the Iranian embassy in central Baghdad, Iraqi independent al-Sharkiya TV channel reported. In Diyala province, gunmen suspected of belonging to the al-Qaeda terrorist network stopped a mini-bus carrying 14 people, including women and children, at a fake checkpoint in Khalis district, 15 kilometres north Baquba, reports said. The militants took the passengers to an unknown location, according to VOI. Diyala and its capital Baquba, about 60 kilometres south-east of Baghdad, has been a flashpoint of insurgency by Iraqi militant groups backed by al-Qaeda. A large-scale security offensive mounted by US and Iraqi troops drove insurgents into the nearby villages and surrounding countryside in June.