The WikiLeaks website has crashed in an apparent cyberattack after the accelerated publication of tens of thousands of once-secret US State Department cables by the anti-secrecy organisation raised new concerns about the exposure of confidential American embassy sources.
"WikiLeaks.org is presently under attack," the group said on Twitter. An hour later, the site and the cables posted there were inaccessible.
WikiLeaks later updated its Twitter account to say that it was "still under a cyberattack" and directed followers to search for cables on a mirror site or a separate search system, cablegatesearch.net.
The apparent cyberattack comes after current and former American officials said the recently-released cables - and concerns over the protection of sources - are creating a fresh source of diplomatic setbacks and embarrassment for the Obama administration.
The Associated Press reviewed more than 2,000 of the cables recently released by WikiLeaks. They contained the identities of more than 90 sources who had sought protection and whose names the cable authors had asked to protect.
Officials said the disclosure in the past week of more than 125,000 sensitive documents by WikiLeaks, far more than it had earlier published, further endangered informants and jeopardised US foreign policy goals. The officials would not comment on the authenticity of the leaked documents but said the rate and method of the new releases, including about 50,000 in one day alone, presented new complications.
"The United States strongly condemns any illegal disclosure of classified information," US State Department spokeswoman Victoria Nuland said.
"In addition to damaging our diplomatic efforts, it puts individuals' security at risk, threatens our national security and undermines our effort to work with countries to solve shared problems. We remain concerned about these illegal disclosures and about concerns and risks to individuals."
WikiLeaks hit back at the criticism even as its website came under cyberattack.
"Dear governments, if you don't want your filth exposed, then stop acting like pigs. Simple," the group posted on Twitter.