The Wikileaks files reveal the activities of about 160 companies in 25 countries which develop technologies to allow the tracking and monitoring of individuals by their mobile phones, email and Internet browsing histories.
"Today we release over 287 files documenting the reality of the international mass surveillance industry -- an industry which now sells equipment to dictators and democracies alike in order to intercept entire populations," Assange told reporters in London.
He said that in the last 10 years it had grown from a covert industry which primarily supplied government intelligence agencies such as the NSA in the United States and Britain's GCHQ, to a huge transnational business.
Assange has been in Britain for the past year fighting extradition to Sweden for questioning on allegations of rape and sexual assault, living under tight bail conditions. His case is due to come up again on Monday.
The documents on the website include manuals for surveillance products sold to repressive Arab regimes. They have come to light in part from offices ransacked during uprisings in countries such as Egypt and Libya earlier this year, as well as investigative work by WikiLeaks and its media and campaigning partners.
"These systems that are revealed in these documents show exactly the kind of systems that the Stasi (East Germany's secret police) wished they could have built," said Jacob Appelbaum, a former WikiLeaks spokesman and computer expert at the University of Washington.
"These systems have been sold by Western companies to places for example like Syria, and Libya and Tunisia and Egypt. These systems are used to hunt people down and to murder."
Experts who worked on the release warned that at present the industry was completely unregulated. "Western governments cannot stand idly by while this technology is still being sold," said Eric King, from the Privacy International campaign group.
It is the first time WikiLeaks has released documents since it announced on October 24 that it had been forced to suspend publishing classified files due to a funding blockade that saw its revenues plunge by 95 %.