The UN's call for probe came after whistle-blowing website WikiLeaks released nearly 400,000 secret American documents on Iraq war chronicling graphic accounts of torture, killing of civilians and Iran's role in the conflict.
The call by UN's chief investigator on torture, Manfred Nowak, came as Phil Shiner, human rights specialist at Public Interest Lawyers in the UK, warned that some of the deaths documented in the Iraq war logs could have involved British forces and would be pursued through the UK courts.
According to a report in the British daily The Guardian, which has analysed the 400,000 documents, found 15,000 previously unreported civilian deaths.
Nowak demanded a public inquiry into allegations that British troops were responsible for civilian deaths during the conflict.
Nowak said the Obama administration had an obligation to investigate them if the "classified military leak" pointed to clear violations of the UN Convention Against Torture, according to the British newspaper.
He said it would be up to the Obama administration to launch an "independent and objective" investigation with a view not only to "bring the perpetrators to justice but also to provide the victims with adequate remedy and reparation".
The logs show how US authorities failed to investigate hundreds of reports of abuse, torture, rape and murder by Iraqi police and soldiers whose conduct appears to be systematic and generally unpunished, the report in the British daily said.
The logs paint a disturbing picture of the relationship between US and Iraqi forces. Nowak underlined that the UN human rights agreements made it obligatory on the parts of states to criminalise all forms of torture, whether directly or indirectly, and probe any allegations of abuse.
Nowak said the Obama administration had a legal and moral obligation to fully investigate credible claims of US forces' complicity in torture.
The latest leaked documents chronicling the Iraq war from 2004 to 2009 provide a new picture of how many Iraqi civilians were killed, open a new window on the role that Iran played in supporting Iraqi militants and give many accounts of abuse by Iraqi army and police, said 'The New York Times', one of the news organisations which got early access to the papers.
