Chelsea Manning, the transgender army private jailed for one of the largest leaks of classified documents in US history, was released from prison today, a US Army spokeswoman said.

Manning "has been released from the United States Disciplinary Barracks" at Fort Leavenworth, Kansas, spokeswoman Cynthia Smith said in a brief statement.

In July 2010, Manning - then a male soldier known as Bradley - was arrested over the release of a huge trove of more than 700,000 classified military and diplomatic documents via WikiLeaks.

Manning, now 29, was serving a 35-year sentence for the leak but president Barack Obama commuted her sentence before leaving office and she was released after seven years in prison.

Manning attempted suicide twice last year alone and went on a hunger strike to denounce disciplinary measures to which she was subjected, including stints in solitary confinement.

"Two more days until the freedom of civilian life," Manning tweeted Monday. "Now hunting for private #healthcare like millions of Americans."