A US soldier in Iraq has been arrested for allegedly leaking classified information to whistleblower website WikiLeaks, including video of a helicopter strike in Baghdad and US diplomatic cables.

Specialist Bradley Manning, 22, who was deployed at a base near Baghdad, is in "pre-trial confinement for allegedly releasing classified information and is currently confined in Kuwait," US Forces Iraq said in a statement.

Pentagon spokesman Bryan Whitman said investigators were probing allegations that Manning supplied classified video and 260,000 secret diplomatic cables to WikiLeaks, as first reported by Wired.com, the website of technology magazine Wired.

"I think that's why the Criminal Investigative Division is taking a very scrupulous look at this," Whitman told reporters here.

Wired.com said Manning, of Potomac, Maryland, was arrested nearly two weeks ago by the US Army's Criminal Investigation Division at Forward Operating Base Hammer, 40 miles (64 kilometers) east of Baghdad.

Manning, who was serving with the 2nd Brigade 10th Mountain Division, was turned in late last month after boasting to a former computer hacker in an online conversation that he had leaked video of a 2007 US military helicopter strike to WikiLeaks, Wired said.

WikiLeaks released video in April of the Apache helicopter attack in Baghdad which killed two employees of the Reuters news agency and a number of other people.

WikiLeaks said at the time that it had obtained the video "from a number of military whistleblowers" but did not provide any further information about how it got ahold of the footage, which it posted at Wikileaks.org and on YouTube.

Manning reportedly said he had leaked other material to WikiLeaks, including separate video of a 2009 air strike in Afghanistan, a classified Army document evaluating Wikileaks as a security threat and classified US 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," Wired quoted Manning as writing.

Wired said it could not confirm WikiLeaks had received the classified cables. It said a single diplomatic cable appeared on the site in February concerning a meeting between the US embassy and the government of Iceland.

WikiLeaks said in a message on its Twitter feed that "allegations in Wired that we have been sent 260,000 classified US embassy cables are, as far as we can tell, incorrect."

Spokesman Philip Crowley said the State Department would take a leak of classified documents "seriously."

"It has particular impact in terms of revealing what we call sources and methods, compromising our ability to provide government leaders with the kind of analysis that they need to make informed decisions," Crowley said.

WikiLeaks said that "if" Manning is the "whistleblower then, without doubt, he's a national hero."

Wired said Manning had been in touch with former hacker Adrian Lamo, who contacted Army investigators and FBI agents after being told of the leaks.

"I wouldn't have done this if lives weren't in danger," Lamo told Wired about turning Manning in to the authorities.

"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 said.

WikiLeaks, run by Sunshine Press, describes itself as a "non-profit organization funded by human rights campaigners, investigative journalists, technologists and the general public."