Chelsea Manning, the US soldier imprisoned for leaking classified files to pro-transparency site WikiLeaks, attempted to take her own life last week, her lawyers say.

"Last week, Chelsea made a decision to end her life," attorneys Chase Strangio, Vincent Ward and Nancy Hollander said in a joint statement on Monday.

The lawyers said Ms Manning, 28, was under close supervision and was expected to remain on that status for several weeks.

The statement confirmed earlier media reports that said Ms Manning's hospitalisation last week near the US Disciplinary Barracks at Fort Leavenworth, Kansas, resulted from a suicide attempt.

They said the US military committed a "gross breach of confidentiality" for revealing her "personal health information" and hospitalisation to the media.

The Pentagon did not immediately respond to a request for comment. The US Army had not officially confirmed the hospitalisation was due to a suicide attempt.

Ms Manning, a former intelligence analyst in Iraq, is serving a 35-year sentence after a 2013 military court conviction of providing more than 700,000 documents, videos, diplomatic cables and battlefield accounts to WikiLeaks. It was the biggest breach of classified materials in US history.

Among the files that Ms Manning turned over to WikiLeaks in 2010 was a gunsight video of a US Apache helicopter firing at suspected Iraqi insurgents in 2007. A dozen people were killed, including two Reuters news staff.

Ms Manning in May appealed to a military court to overturn her court-martial conviction.

Her lawyers have said she was held in unlawful pre-trial detention for nearly a year and that her punishment is excessive, a claim civil liberties and government transparency advocates have echoed.

Reuters