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 Taliban.
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 given to the New York Times, the Guardian and the German news magazine, Der Spiegel.
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 2004 to 2009, before President Obama "announced a new strategy with a substantial increase in resources for Afghanistan".