US says Wikileaks could 'threaten national security'
The United States has condemned as "irresponsible" the leak of 90,000 military records, saying publication could threaten national security.
The documents released by the Wikileaks website include details of killings of Afghan civilians unreported until now.
Three news organisations had advance access to the records, which also show Nato concerns that Pakistan and Iran are helping the Taliban in Afghanistan.
Pakistan has denied claims its intelligence agency backed the group.
The Pakistani presidential spokeswoman, Farahnaz Ispahani, said the leaks might be an attempt to sabotage the new strategic dialogue between the US and Pakistan.
A spokesman for Afghan President Hamid Karzai said he was "shocked" at the scale of the leaks, but thought that "most of this is not new".
The huge cache of classified papers - posted by Wikileaks as the Afghan War Diary - is one of the biggest leaks in US history. It was also given in advance to the New York Times, the Guardian and the German news magazine, Der Spiegel.
The founder of Wikileaks, Julian Assange, said he had no reason to doubt the reliability of the reports.
"When we publish material, what we say is: the document as we describe it is true," he said at a news conference in London.
"We publish CIA reports all the time. They are legitimate reports, but they don't mean the CIA is telling the truth."
Mr Assange said there was no one overarching revelation to come out of the cache.
"The real story of this material is that it's war - it's one damn thing after another," he said. "It is the continuous small events, the continuous deaths of children, insurgents, allied forces, the maimed people. Search for the word 'amputation' in this material, or 'amputee', and there are dozens and dozens of references."
He compared the impact of the released material to the opening of the archives of the East German secret police, the Stasi.
In a statement, US National Security Adviser Gen James Jones said such classified information "could put the lives of Americans and our partners at risk".
He said the documents covered the period from January 2004 to December 2009, before President Barack Obama "announced a new strategy with a substantial increase in resources for Afghanistan".
But Mr Assange was sceptical, saying: "A new policy by Obama doesn't mean new practice by the US military."
He also said Wikileaks had "tried hard to make sure that this material does not put innocents at harm".
"All the material is over seven months old so is of no current operational consequence, even though it may be of very significant investigative consequence."
After being asked repeatedly by reporters whether he believed some of the incidents described in the documents constituted war crimes, Mr Assange said: "It is up to a court to decide, clearly, whether something is, in the end, a crime."
"That said, prima facie, there does appear to be evidence of war crimes in this material," he added.
He cited as an example an attack in June 2007 by a secret US special forces unit, Task Force 373, which used a Himars (High Mobility Artillery Rocket System) to begin a raid on a compound where a senior al-Qaeda leader, Abu-Laith al-Libi, was thought to be hiding. Seven children died.
The Nato-led International Security Assistance Force acknowledged the deaths of the children at the time, but stated that coalition troops had attacked because of "nefarious activity" there.
It did not mention they had targeted al-Libi nor used a Himars before any shots had been fired at them, and has not commented on the details included in the Wikileaks papers.
Pakistan's government meanwhile denied claims its Inter-Services Intelligence (ISI) agency backed the Taliban in the war in Afghanistan.
One of the leaked documents refers to an alleged meeting between insurgents and the former ISI chief, Lt Gen Hamid Gul.
He dismissed the Wikileaks material as "pure fiction which is being sold as intelligence".
"It's not intelligence," Gen Gul, who ran the agency from 1987 to 1989, told the BBC. "It may have a financial angle to it but more than that it is not hardcore [intelligence]. I'm an old veteran. I know."
"It is all wrong. It's precisely as their intelligence regarding Saddam Hussein keeping weapons of mass destruction in his closet," he added. "This is all based on falsehood. That is why they are not winning, because they have no cause."
Pakistani officials have denied that Gen Gul still works for the ISI.
The reports also suggest:
The Taliban has had access to portable heat-seeking missiles to shoot at aircraft
A secret US unit of army and navy special forces, Task Force 273, has been engaged on missions to "capture or kill" top insurgents
Many civilian casualties - caused by Taliban roadside bombs and Nato missions that went wrong - have gone unreported
Iran is engaged in an extensive covert campaign to arm, finance and equip the Taliban and Afghan warlords allied to al-Qaeda
But the head of the Foreign Relations Committee in the US Senate said the leak came at a "critical stage" for US policy in the region.
"However illegally these documents came to light, they raise serious questions about the reality of America's policy toward Pakistan and Afghanistan," Democratic Senator John Kerry said.
UK Foreign Secretary William Hague said he did not think the leaks would damage the international effort in Afghanistan.
Wikileaks says it delayed the release of about 15,000 reports from the archive as part of a "harm minimisation process demanded by our source".
The Guardian and the New York Times say they had no contact with the original source of the leak, but spent weeks cross-checking the information.
Earlier this year, Wikileaks posted a video on its website which it said showed the killings of civilians by a US military helicopter in Baghdad in 2007.
A US military analyst, Bradley Manning, is awaiting trial on criminal charges of leaking the video.
A former hacker, Adrian Lamo, said Mr Manning boasted to him about handing over military videos and 260,000 classified US embassy messages to Wikileaks.
Wikileaks has refused to identify its source for the video or the US military documents.
Meanwhile, Nato says it is investigating reports that as many as 45 civilians died in an air strike in Helmand province on Friday. A BBC journalist has spoken to villagers in Regey who said they witnessed the incident.
A Nato spokesman said international forces went to great lengths to avoid civilian casualties.