The prime suspect in the theft of more than 600 computers that were used to mine bitcoin has escaped from an Icelandic prison and travelled to Sweden on a plane carrying the country's prime minister.

Sindri Thor Stefansson climbed out of a window at the low security Sogn open prison, a low-security facility which has no fences.

Guards only realised he was gone, a long time after he had boarded the Icelandair flight bound for Stockholm Arlanda airport at Keflavik Airport, using another person's passport.

A spokesperson for the Prime Minister’s Office in Iceland confirmed to The Independent that Katrin Jakobsdottir was aboard the same flight. She has not commented on the escape.

A Swedish police spokesperson said no arrests have been made but an international arrest warrant has been issued.

“He had an accomplice,” police chief Gunnar Schram told local news outlet Visir. “We are sure of that.”

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Mr Stefansson was arrested in February, along with 11 other people suspected of raids on data centres in the country, which local media has dubbed “the Big Bitcoin Heist.”

The stolen computers are yet to be recovered, but experts have warned that recovering the stolen cryptocurrency may not be possible even if the mining machines are found.

“Unlike traditional banking mechanisms, blockchain currencies can be stolen and moved to thieves accounts with no means of recovery. Nothing can bring it back,” said Dr Kevin Curran, a professor of cybersecurity at Ulster University and senior IEEE member.

“This is a real and ever-present danger with cryptocurrencies and there have been ever-increasing incidents of coins being stolen, as seen recently.”

Iceland is popular among bitcoin miners for its abundant renewable energy that makes mining cryptocurrency both cheap and environmentally friendly.