Kristinn Hrafnsson, editor-in-chief of WikiLeaks, accused Ecuador authorities of gathering thousands of photographs and videos, which then found their way into the hands of a group in Spain, who were demanding $3 million (2.7 million euros) not to publish them.

"We learned some individuals in Spain were passing around information, that they had a massive trove of documents... from inside the embassy," he told reporters in London.

"I asked them what documents they had and I got an email back. He said 'this material has a price'."

The documents include thousands of photographs and gigabytes of video footage showing Assange meeting with lawyers and visitors and of him receiving a medical check-up.

"It's not hard to see that as extortion," said Hrafnsson, adding that the Spanish police had opened an investigation.

"Of much greater concern is this material gathering and spying by the Ecuadorian government," he said, calling it "illegal and extremely unethical".