Mosul: An initial investigation of a recent airstrike believed to have killed more than 200 civilians in Mosul found it was conducted by the US-led coalition at the request of Iraqi security forces, the Pentagon said on Saturday.

Witnesses said the airstrike killed hundreds of residents on Baghdad Street in west Mosul's Aghawat Jadidah neighbourhood on March 17, including many women and young children. On Friday, in an area where apartment blocks were reduced to rubble, at least 50 bodies could be seen, including those of pregnant women, children and newborns.

Residents carry the bodies of several people killed during fights between Iraq security forces and Islamic State on the western side of Mosul. Credit:AP

On Saturday, a day after announcing that the incident was under investigation, Pentagon officials released a statement saying the coalition had targeted Islamic State fighters and equipment in the area on March 17, "at the location corresponding to allegations of civilian casualties".

The coalition said that it takes allegations of civilian casualties seriously and that a formal Civilian Casualty Credibility Assessment of the airstrike and the civilian toll is under way.