Manning's attorneys described how her prison conditions - including a period of solitary confinement for a previous suicide attempt - have contributed to their client's fragile mental health.

But lawyers Vincent Ward and Chase Strangio declined to divulge details of the second suicide attempt on October 4 at a military prison at Kansas' Fort Leavenworth.

"After her July suicide attempt, I watched her begin to piece her life and spirit back together, only to have that shattered by the disciplinary proceedings brought against her, and then the unannounced initiation of her term of punishment last month," Strangio wrote in a statement.

"She has repeatedly been punished for trying to survive and now is being repeatedly punished for trying to die."

Strangio also described Manning's treatment in prison as "demoralizing and destabilizing" for her health.

Manning was taken to hospital on July 5 following a suicide attempt and was later sentenced to 14 days in solitary confinement as punishment. Seven of those days were suspended.

In September, she began a hunger strike, protesting at what she said was bullying by prison and US authorities. Four days later, the US Army agreed to provide her treatment for her gender dysphoria, including surgery recommended in April by her psychologist. 

In 2014, the American Civil Liberties Union (ACLU) sued the US Department of Defense over its refusal to treat the mismatch between Manning's biological sex and gender identity.

Manning, who was born male, was employed an intelligence analyst for the US army in Iraq, and was arrested in 2010 under the name Bradley Manning.

The 28-year-old was convicted by a military court three years later of leaking more than 700,000 secret and sensitive documents to WikiLeaks. A day after sentencing, Manning's lawyers requested that their client was now identifying as a woman named Chelsea.

The material included diplomatic cables, details on airstrikes in Iraq and Afghanistan, along with army reports about both US-led invasions.

On Friday, Wayne Hall, an Army spokesman, said medical privacy laws barred him from discussing the latest incident.

mm/kl (AFP, AP, Reuters)