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.