Julian Assange was arrested in London last year after Sweden issued an arrest warrant [Reuters]

Lawyers for Julian Assange, founder of whistleblowing website Wikileaks, have lodged an appeal against an order for his extradition to Sweden, where he faces questioning over allegations of rape and sexual molestation.

The 39-year-old Australia has described last week's decision by a British court to extradite him as the "result of the European arrest warrant system run amok".

Assange said he is prepared for a lengthy legal battle to fight the ruling, which analysts say he may be able to take as high as the European Court of Human Rights.

Officials at the High Court in London said they had received the appeal papers on Thursday, but no date had been set for a hearing.

Sexual misconduct claim

Assange faces questioning in Sweden over claims of sexual misconduct made by two women he met during a visit to Sweden last August.

The website founder denies wrongdoing and says he had consensual sex with the two women.

His lawyers have argued that Assange, if extradited to Sweden, risks being handed over to the United States where they say he could face imprisonment or the death penalty.

Assange's appeal on Thursday also came as the US authorities lodged an additional 22 charges against Bradley Manning, the US soldier accused of passing confidential military files to WikiLeaks, including a video showing forces firing on Iraqi civilians.

The new charges include the accusation of "aiding the enemy," which carries a potential death sentence.

WikiLeaks angered Washington officials last year by releasing thousands of secret government documents from diplomats around the world.

Assange currently remains on bail in Britain, living under curfew at a supporter's rural mansion in eastern England.