The US Marines are drawing up plans to send back to Iraq at least some reserve combat battalions that have already served one tour there, the first time such units would be returned to the war.

A music video posted to the internet, telling a tale about a US Marine killing members of an Iraqi family, is being condemned by an Islamic group and investigated by the Marine Corps.

The deaths of as many as two dozen Iraqi civilians and an ensuing cover-up threaten to do more harm to US efforts in Iraq than even the Abu Ghraib prison scandal, a prominent congressman and war critic says.