WikiLeaks founder Julian Assange leaves Southwark Crown Court after being sentenced in London, Britain, May 1, 2019. REUTERS/Henry Nicholls

GENEVA (Reuters) - United Nations human rights experts voiced concern on Friday at what they called the “disproportionate sentence” of 50 weeks in prison imposed on WikiLeaks founder Julian Assange for skipping bail in Britain.

Assange is being held in the high-security Belmarsh prison “as if he were convicted for a serious criminal offence”, the U.N. working group on arbitrary detention said in a statement, adding that this “appears to contravene principles of necessity and proportionality”. It described the skipping bail charge as a relatively “minor violation”.

The group, composed of five independent experts, issued an opinion in 2015 that Assange - holed up at the time at the Ecuadoran Embassy in London after skipping bail to avoid extradition to Sweden to face an allegation of rape - was being arbitrarily detained. Assange has denied the rape allegations.