An unemployed London computer systems administrator was arrested on Tuesday relating to charges of hacking US government computers in 2001.

Gary McKinnon, 39, was taken into custody at his home in northeast London at 6.30pm and transferred to a central London police station. An extradition hearing was set for Wednesday, according to a spokeswoman for the Metropolitan Police.

Although McKinnon was formally charged in the US in November 2002, London police only received the extradition warrant recently, the spokeswoman said.

McKinnon, known by his hacker handle Solo, is charged with seven counts of computer fraud and related activity in Virginia stemming from a year-long hacking spree. The extradition warrant alleges that he gained illegal access and made unauthorised modifications to 53 computers belonging to Nasa, the US Army, the US Navy, the US Department of Defence and the US Air Force between 1 February 2001 and 19 March 2002.

Once inside a network, McKinnon is alleged to have installed remote administration and hacker tools, copied password files and other sensitive but unclassified files, and deleted user accounts and other critical system files. In at least one instance, McKinnon's hacking activity allegedly caused a major military network in Washington to shut down for three days in February 2002.

"The significance of this case is that [with] his access to these records, he was able to impair the integrity of the data on these systems," said Paul J. McNulty, US Attorney for Virginia, at the time of the indictment. McKinnon allegedly "scanned tens of thousands of systems" before taking advantage of known vulnerabilities in Microsoft's Windows operating system installed on the targeted computers.