Former US Army intelligence analyst Chelsea Manning attempted suicide inside a jail in Alexandria, Virginia, on Wednesday and was admitted to hospital just days before a federal judge is scheduled to hear a motion to release her from custody, her lawyers said.

Jail officials responded to an incident involving Manning at 12.11pm local time at the Alexandria Adult Detention Centre, according to a statement released by Alexandria Sheriff Dana Lawhorne.

Chelsea Manning in 2018. Credit:AP

"It was handled appropriately by our professional staff and Ms Manning is safe," Lawhorne's statement said.

Manning, who leaked hundreds of thousands of classified documents to WikiLeaks in 2010, has been held for about a year for refusing to testify to a federal grand jury investigating the anti-secrecy website.