The WikiLeaks website crashed on Tuesday in an apparent cyber attack after the accelerated publication of tens of thousands of State Department cables by the anti-secrecy organisation raised new concerns about the exposure of confidential US embassy sources.
"WikiLeaks.org is presently under attack," the group said on Twitter. One hour later, the site and the cables posted there were inaccessible.
WikiLeaks 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 US president Barack Obama administration.
It was not immediately clear who was behind the attack.
WikiLeaks fired 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.