The 49-year-old Australian, who has been in high-security Belmarsh Prison for 16 months, is wanted over the publication of hundreds of thousands of classified documents in 2010 and 2011.

On Monday, he was arrested in the cells at the Old Bailey over a new US indictment, containing 18 charges, lodged in June.

They add detail of alleged hacking plotters, which Assange and others at WikiLeaks were said to have recruited.

Mark Summers QC, defending, said the "fresh allegations at the 11th hour" were brought without warning or explanation, giving the defence no time to properly prepare a response before the extradition hearing.

He highlighted the difficulties Assange faced in speaking to his lawyers in the midst of ongoing restrictions.

"It would be an impossible task for the defence to deal with these fresh allegations in any meaningful way in the time that has been afforded to them and that time is a matter of weeks in respect of which we are provided absolutely no explanation for the late arrival of these matters."

He added: "What is happening is abnormal, unfair and liable to create injustice if allowed to continue."

District Judge Vanessa Baraitser rejected the defence bid to "excise" the allegations, saying: "These are issues which must take place in the context of considering the extradition request and not before it."

Earlier, Assange stood in the dock of Court 10, clean shaven with spectacles perched in his short cropped hair, wearing a smart dark suit, maroon tie and white shirt.

He spoke to state he does not consent to extradition after confirming his name and date of birth at the start of the hearing.

The charges against him include plotting to hack computers and conspiring to obtain and disclose national defence information.

The allegations include that Assange conspired with army intelligence analyst Chelsea Manning to crack a scrambled password, known as a "hash", to a classified US Department of Defence computer.

If convicted, he faces a maximum possible penalty of 175 years in jail.

Assange's legal team has accused the Trump regime of targeting him for "political" reasons after WikiLeaks exposed alleged war crimes and human rights abuses.

Dozens of supporters, including his father John Shipton and fashion designer Dame Vivienne Westwood, protested outside court before the hearing began.

Assange's partner Stella Moris, who has two children with him, was in court after visiting Downing Street in a bid to deliver a Reporters Without Borders petition against the extradition, which has been signed by around 80,000 people.

"To the boys, Julian has become a voice on the telephone, not their father whom they can see and hug," she said.

"It is heartbreaking to think that if Julian is extradited and put in a US super-max prison, the boys will never get to know their father and he will never see them grow up.

Dozens of witnesses are expected to be called to give evidence over four weeks.

Assange has been held on remand in Belmarsh Prison since last September after serving a 50-week jail sentence for breaching his bail conditions while he was in the Ecuadorian embassy in London for almost seven years.

Australian Associated Press