Washington: A US soldier accused of forwarding information to whistle-blower website WikiLeaks has been forced to sleep naked in a detention facility in Virginia, the Defence Ministry acknowledged.

Pentagon spokesman Col Dave Lapan confirmed reports that Bradley Manning, army intelligence analyst, who has been confined at a marine base in Virginia, has been forced to sleep naked. However, Lapan refused to give the rationale behind it due to privacy reasons.

"For privacy reasons, we can't talk about the rationale," Lapan said.

In custody for seven months, Manning, 23, was charged with the allegations that he introduced unauthorised software onto government computers to extract classified information and transmitted the classified data for public release. Manning was early this week slapped with additional 22 charges.

He is being treated like every other detainee of that category is treated, Lapan said, but ruled out that the suspect is under a suicide watch.

"The way he is being treated in the facility is consistent with his circumstances. We do not treat him any differently because he is in the news," Lapan said.

Pentagon spokesman Lapan's comments came as Manning's lawyer said that his client was "forced to strip naked" in his prison cell on Wednesday and Thursday.

Manning "was forced to strip naked in his cell again last night... As with the previous evening, Quantico Brig (marine base) guards required him to surrender all his clothing," lawyer David E Coombs wrote on his blog on Friday.

"Manning then walked back to his bed and spent the next seven hours in humiliation," he said. According to First Lieutenant Brian Villard, a Marine spokesman, the decision was "not punitive" and done in accordance with the Brig rules.

"I can confirm that it did happen, but I can't explain it to you without violating the detainee's privacy."

Geoffrey Morrell, the Pentagon Press Secretary, said on MSNBC that Manning's confinement was due to "the seriousness of the charges he's facing, the potential length of sentence, the national security implications."

Lawyer Coombs, however, blasted the decision. He noted that Manning is already being monitored – both by direct observation and video - at all times.