U.S. officials have condemned the release of thousands of secret military and intelligence reports about the war in Afghanistan by the website WikiLeaks.

The nearly 77,000 documents, released Sunday, reveal new details about the war in Afghanistan, including the close relationship of the Pakistani military with Afghan insurgents. WikiLeaks plans to publish another 15,000 soon, bringing the total released to 92,000.

Soldiers from the Royal Canadian Regiment patrol the Panjwaii district, southwest of Kandahar city, on May 20. (Nikola Solic/Reuters)

The documents also describe numerous accounts of brutality, corruption, extortion and kidnapping committed by members of the Afghan police force. Another revelation is that the Taliban used heat-seeking missiles to down a helicopter in 2007, possibly killing a Canadian soldier.

The documents were written by soldiers and intelligence officers, WikiLeaks said.

Foreign Affairs Minister Lawrence Cannon slammed the documents' release, saying it could endanger the lives of Canadian Forces serving in Afghanistan.

In a statement, U.S. National Security Adviser James Jones said the release "could put the lives of Americans and our partners at risk, and threaten our national security."

"These irresponsible leaks will not impact our ongoing commitment to deepen our partnerships with Afghanistan and Pakistan; to defeat our common enemies; and to support the aspirations of the Afghan and Pakistani people," he said.

Pakistan's ambassador to the United States on Monday downplayed the documents' release, saying many of the reports are based on conjecture and rumour.

"Some of these have already been proved wrong in the past, and some are just hearsay or statements by individuals," Husain Haqqani said. "The fact of the matter is, this is routine and I don't think as big a deal as it's being made out to be."

Documents 'fiction'

The New York Times and Guardian newspapers were given early access to the records, as was German weekly Der Spiegel.

The New York Times said the documents reveal that only a short time ago, there was far less harmony in U.S. and Pakistani exchanges.

The Times said the "raw intelligence assessments" by lower level military officers suggest that Pakistan "allows representatives of its spy service to meet directly with the Taliban in secret strategy sessions to organize networks of militant groups that fight against American soldiers in Afghanistan, and even hatch plots to assassinate Afghan leaders."

The Guardian, however, interpreted the documents differently, saying they "fail to provide a convincing smoking gun" for complicity between the Pakistan intelligence services and the Taliban.

'Militaries keep information secret to prosecute the war but also to hide abuse.' —WikiLeaks founder Julian Assange

Maj.-Gen. Athar Abbas, spokesman for Pakistan's army, which commands the spy agency, was not reachable for comment Monday on the intelligence reports.

But Hamid Gul, a former head of the spy agency who is mentioned many times throughout the released reports, denied allegations that he was working with the Taliban.

"These leaked documents against me are fiction and nothing else," said Gul.

Defending the release

WikiLeaks founder Julian Assange told The Guardian Monday the website is working through a backlog of further secret material and is expecting a "substantial increase in submissions" from whistleblowers.

Assange believes the documents show clear evidence of war crimes.

Speaking to reporters in London, the normally reclusive Assange said, "It is up to a court to decide really if something in the end is a crime. That said … there does appear to be evidence of war crimes in this material."

Assange compared the impact of the released material to the opening of the East German secret police archives.

"This is the equivalent of opening the Stasi archives," he said.

WikiLeaks has been publishing leaked government documents since it first appeared online in December 2006. It focuses on documents that allege "government and corporate misconduct," according to its website.

"Militaries keep information secret to prosecute the war but also to hide abuse," Assange said, defending the documents' release.

"There is a military argument for keeping some information secret that is very timely — as an example, where troops are about to deploy — but that information expires quickly," he said.

Possible risk to NATO troops: analyst

The latest documents cover the period from January 2004 to December 2009.

The information is not new for anyone who's been tracking the conflict, military analyst Mercedes Stephenson told CBC News.

But Stephenson said some of the information contained in the documents, including times and dates of attacks, damage to vehicles and number of injured, could pose a risk to NATO troops fighting in Afghanistan.

"There is a reason certain information is not released by coalition forces and it's because it allows the Taliban to judge the success of … or to figure out coalition tactics," Stephenson said. "And that jeopardizes soldiers' lives."

WikiLeaks made news in April when it released a classified U.S. military video showing a 2007 helicopter attack that killed a dozen people in Baghdad, including a driver and photographer working for the Reuters news agency.

The U.S. military has said it traced both leaks to Pte. 1st Class Bradley Manning, a 22-year-old intelligence analyst who had been working at an army forces operating base in Baghdad.

With files from The Associated Press