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US military authorities have arrested an intelligence analyst who allegedly passed classified material to Wikileaks following a tip-off from a former hacker.

Specialist Bradley Manning, 22, of Potomac, Maryland, has reportedly been held in Kuwait for almost two weeks on suspicion of leaking a video of a helicopter attack in Baghdad in 2007 that killed civilians.

Manning had been stationed at Forward Operating Base Hammer, 40 miles east of the Iraqi capital, Wired reports. The US Army's Criminal Investigation Division acted on a tip-off from Adrian Lamo, a former hacker who Manning recently contacted online, apparently prompted by a Wired profile.

Manning allegedly boasted to Lamo he had leaked the video, as well as footage of another attack, a secret counter-intelligence briefing about Wikileaks, and a cache of 260,000 diplomatic cables.

"Hillary Clinton, and several thousand diplomats around the world are going to have a heart attack when they wake up one morning, and find an entire repository of classified foreign policy is available, in searchable format, to the public," Manning wrote.

Their conversations took place over IM and email. Lamo says contacted the Army and FBI and gave them copies of his communications with Manning out of fear for safety in Iraq.

"I wouldn't have done this if lives weren't in danger," he said. "He was in a war zone and basically trying to vacuum up as much classified information as he could, and just throwing it up into the air."

Lamo is today battling criticism of his actions on Twitter. The former hacker, who has Asperger's, is claiming a Facebook post by Manning would have alerted authorities if he had not.

"I didn't break the story; Manning did with his Facebook post. It was only a matter of time from there, so I went whole-hog," he wrote.

In their private online conversations, Manning, who had Top Secret security clearance, told Lamo that he spent more than a year sifting through material on classified government networks containing "incredible things, awful things". He was reportedly reassured that Wikileaks could protect his identity by its release of the 9/11 pager message archive, which he recognised as coming from inside the NSA, the most secure of the US intelligence agencies.

Manning has not yet been formally charged.

In the US Army's counter-intelligence briefing about Wikileaks, allegedly leaked by Manning, analysts noted that one way to staunch the flow of classified material to the site would be to expose a leaker.

"The identification, exposure, or termination of employment of or legal actions against current or former insiders, leakers, or whistleblowers could damage or destroy this center of gravity and deter others from using Wikileaks.org to make such information public," their report said. ®

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