WASHINGTON -- Hundreds of supporters of Bradley Manning converged at Leavenworth, Kan., Saturday to rally for the Army private accused of leaking classified documents to the anti-secrecy group WikiLeaks.

Gathered outside the prison where Manning is currently being held, protesters denounced Manning's treatment and called on the White House to drop all charges against him.

"PFC Bradley Manning is a fellow soldier," Brian Wolfe, a Kansas-based Army Veteran who served in Operation Iraqi Freedom, said in an email statement. "If a fellow soldier is punished for taking his oath to defend the constitution seriously, what does that mean for our military and for our democracy?"

The event marked the first public rally in support of Manning since he was transferred to Fort Leavenworth in April after being imprisoned for nine months on the Quantico Marine Corps Base in Virginia.

While detained at Quantico, Manning was forced to sleep naked in a military jail after a commander of the brig ordered his clothes be taken away for a full seven hours. He was also forced to stand naked outside his cell in front of the rest of the clothed inmates until he passed inspection and was given his clothes back.

"The information Bradley Manning is accused of releasing should have been in the public domain. Whoever revealed it is an American hero." said Jeff Paterson, a Steering Committee member of the Bradley Manning Support Network who also spoke at the rally, in a statement. "Our leaders in Washington need to return to American principles of transparent and accountable government. That starts with protecting -- not prosecuting -- whistle-blowers and dropping all charges against Bradley Manning."

Manning stands accused of revealing tens of thousands of classified U.S. military and State Department documents that some believe helped to catalyze democratic revolts across the Middle East this spring. His trial is slated to begin this summer.