WikiLeaks editor Julian Assange has been ordered to stay in a British prison despite reaching the end of his 50-week prison sentence.

Assange was due to be released on September 22 after serving his sentence for breaching bail conditions by seeking refuge in the Ecuadorian Embassy in London in 2012.

However, the 48-year-old was told at a court hearing in London last month that he will be kept in Belmarsh prison because of “substantial grounds” for believing he will abscond ahead of a hearing on his possible extradition to the United States.

At a brief hearing at Westminster Magistrates’ Court on Friday, Deputy Senior District Judge Tan Ikram ordered Assange to remain behind bars “for the same reasons as before.”

Assange appeared by video link from Belmarsh and spoke only to confirm his name and age before he was remanded in prison. He is due to appear in court in person at his next hearing on October 21.

“I very much hope we can make some progress on this case,” Judge Ikram told Assange at the end of the five-minute hearing, Reuters reports.

In the US, Assange is charged with possession and dissemination of classified information. If found guilty, he could receive up to 175 years in prison. The activist has long warned that the US would attempt to extradite him after WikiLeaks published leaked material from the Democratic National Committee and Hillary Clinton campaign manager John Podesta’s email account.

WikiLeaks’ also released the notorious ‘Collateral Murder’ video, which shows the US military attacking journalists and civilians in Iraq in July 2007.

Following Friday’s ruling WikiLeaks tweeted: “Six months ago today Assange was illegally arrested in the Ecuadorian embassy, now a political prisoner in Belmarsh where he is not serving any sentence but is awaiting his extradition for publishing the truth and facing 175 years in the USA.”