The Iraqi government has said it will ask the United States for the files of an investigation into allegations that US Marines killed Iraqi civilians in Haditha last year.

Prime Minister Nuri al-Maliki has expressed his hope that the investigation would be fair 'for the sake of all the victims'.

US defence officials have said murder charges may be brought against marines following the investigation into the deaths of 24 civilians in the town.

Mr Maliki, who has said he is losing patience with reports of killings of Iraqi civilians, condemned the suspected massacre in Haditha as a 'terrible crime'.

The US military says it is investigating four other cases in which US troops are alleged to have killed Iraqi civilians.

In one of those probes, US military prosecutors are expected to charge seven marines and a navy serviceman over the death of an Iraqi civilian.

The eight men are being held at Camp Pendleton in California, in connection with the 26 April killing of a Hamandiya man and a subsequent attempt to make him look like an insurgent by placing an AK-47 rifle near his body.

And an investigation is still being conducted into a shooting involving US troops in Ishaqi, north of Baghdad, in March.

Six adults and five children, including an infant, were shot dead in a US raid on a home.  A senior Iraqi police officer said autopsies had showed each had been shot in the head.

Man sentenced over Abu Ghraib abuse

Meanwhile, a US army sergeant convicted of using his dog to assault an inmate at Iraq's notorious Abu Ghraib prison has escaped a prison term or expulsion from the military.

A military jury sentenced Sergeant Santos Cardona, 32, to hard labour without confinement for 90 days and demoted him one rank to specialist fourth class.

Cardona had faced a maximum term of up to three-and-a-half years and a dishonourable discharge.

He becomes the 11th low-ranking soldier to be convicted over the Abu Ghraib scandal.

The Abu Ghraib outcry erupted in 2004 after photographs were published showing US guards mistreating and sexually humiliating prisoners.