Iraqi medical officials said at least 30 people were killed in violence overnight in the Sunni insurgent stronghold of Ramadi in what local police described on Tuesday as a US military raid.
A US military spokeswoman said she would look into the reports. The US commander in the city, 110 km west of Baghdad, said last month he was on the offensive.
An Iraqi police source, speaking on condition of anonymity for fear of reprisals, said US forces raided the al-Dhubat district late on Monday and several houses were destroyed.
In one part of the district, a Reuters reporter saw several bodies of adult men still lying in a street, some being placed in coffins by relatives, and a number of body parts. One small structure was burnt out in that street.
Local residents, who declined to be named for fear of reprisals, said US tanks had fired into the area and that those who died were not militants.
They criticised the US forces and Shi'ite-led Iraqi government. Several said young men gathered to play a traditional street game had been attacked.
Abdullah Salih, a doctor at Ramadi's main hospital, said 35 dead had been brought in and that he believed other bodies had still not been retrieved because access to the area was limited by continuing military operations.
Earlier, another doctor, Kamal al-Ani, said 30 bodies were brought in from the district, along with 17 wounded.