Washington: Bradley Manning, a US serviceman suspected of passing classified information to the whistle-blower website WikiLeaks, is being transferred to a new prison, the Pentagon announced on Wednesday.

"The Army is transferring Private Manning from the pre-trial confinement facility at Quantico to the new Joint Regional Correctional Facility at Fort Leavenworth, Kansas,” Department Of Defence's General Counsel Jeh Johnson said.

Although the transfer comes amidst allegation of mistreatment to Manning, the Pentagon officials denied that this was the reason for his transfer.

23-year-old US Army intelligence officer Manning, who allegedly provided the WikiLeaks with a trove of secret documents, has been imprisoned at Quantico since July 2010.

Manning will return to the Washington area as needed for legal proceedings, as his case remains under the jurisdiction of the US Army's military district of Washington.

Manning's detention conditions, which have included solitary confinement and being forced to sleep naked, have drawn the attention of Amnesty International, the American Civil Liberties Union and Britain. Amnesty International in February called Manning's detention "harsh and punitive" and urged Britain to intervene on his behalf.