A group of online activists have threatened to attack UK government websites if WikiLeaks founder Julian Assange is extradited to Sweden.

Assange was arrested in the UK earlier this week. He is wanted in Sweden on one count of unlawful coercion, two counts of sexual molestation and one count of rape. He is due to appear in court on Tuesday.

The Anonymous group has already launched distributed denial of service (DDOS) attacks on the websites belonging to Mastercard, Visa and the Swedish government, which temporarily brought the sites down. The attacks were thought to be in retaliation for Mastercard and Visa's decision to stop processing payments to WikiLeaks.

WikiLeaks recently started releasing a cache of more than 250,000 sensitive cables sent among members of the US State Department.

Gregg Housh, an American internet activist who previously worked with the hackers, told The Telegraph: "They will go after the weakest links, because they want to see results. They will probably test a few sites and then decide."

The group has been using Twitter to claim responsibility for the distributed denial of service (DDOS) attacks.

One of the hackers told The Telegraph: "It is definitely an information war. The core principle behind it is [that] information is free, governments keep information to themselves, WikiLeaks releases it to the general public and the war occurs."

However, WikiLeaks has distanced itself from the attacks.

"These denial of service attacks are believed to have originated from an internet gathering known as Anonymous. This group is not affiliated with Wikileaks. There has been no contact between any Wikileaks staffer and anyone at Anonymous," Kristinn Hrafnsson from the organisation said on a statement posted the website said.

"WikiLeaks has not received any prior notice of any of Anonymous' actions."

See also: WikiLeaks: China pressured Google on internet censorship