A UK court has approved a US request to extradite an unemployed systems administrator who allegedly caused $700,000 in damage by hacking into US military and government computers.

The hacker claims he was simply looking for data about UFO sitings.

Gary McKinnon, 40, of London, is accused of deleting data and illegally accessing information on US government computers between February 2001 and March 2002. Prosecutors allege McKinnon significantly disrupted government computers, causing damage that threatened US military networks.

British investigators seized McKinnon's computers in March 2002. McKinnon admitted to installing remote-access software on computers he targeted in the US.

The US filed an extradition request after British officials decided not to prosecute McKinnon because the alleged crimes occurred within the US.

McKinnon's attorneys fought extradition, fearing that he could be classed as an enemy combatant and be held indefinitely, awaiting trial by a military court.

UK Trial judge Nicholas Evans rejected arguments that McKinnon could be subjected to torture and inhuman treatment in the US. The US says McKinnon will not be held as an enemy combatant.

Evans referred the case to the UK Secretary of State to decide whether McKinnon will be extradited.

McKinnon will appeal the verdict and remains free on bail. Before leaving the court, he hugged friends and relatives attending the hearing.