An apparent hacker attack crashed the Wikileaks website on Sunday, just as 250,000 leaked US diplomatic despatches were being made public, but news media sites carrying edited versions of the cables remained operational.
The www.wikileaks.org domain was brought down by a method known as distributed denial of service (DDoS), in which a huge number of computers repeatedly demand web pages from the server, shutting out ordinary human users and causing the server to jam.
There was no indication on Sunday who might have mounted the attack.
On the social network Twitter, WikiLeaks announced, "We are currently under a mass distributed denial of service attack."
Media which had advance access to the cables offered many of them via their own websites. The publishing consortium included the Der Spiegel of Germany, The New York Times, the London newspaper The Guardian and El Pais of Madrid.
Julian Assange, the Australian who founded WikiLeaks, meanwhile defended the release.
Speaking on al-Jazeera television, he said the cables told the "diplomatic history" of global affairs and said, "No single individual has even come to harm as a result of anything that we have ever published."
The TV channel said he was speaking to its reporters in Jordan by video link from an undisclosed location on Sunday.