WikiLeaks' website has released a further 400 thousand secret US files which show the United States has known about but failed to investigate cases of prisoner abuse by Iraqi police and soldiers.

The Iraq war files also touch on other themes, including well-known U.S concerns about Iranian training and support for Iraqi militias.

They also offer new details on civilian deaths in the Iraqi conflict. This is the second time WikiLeaks has published classified US military documents.

The first 70,000 files on the Afghan war were posted online in July. The two incidents represent the largest security breaches of their kind in US military history, and have drawn a sharp rebuke from the Pentagon.