The United Arab Emirates has pardoned and will free a British academic sentenced to life in prison for spying after showing journalists a video of him purportedly saying he was a captain in British intelligence.

Authorities made the announcement on Monday about Matthew Hedges in a hastily called news conference in Abu Dhabi, the UAE capital.

They said UAE President Khalifa bin Zayed Al Nahyan issued the clemency for Hedges on Sunday with hundreds of others.

Authorities say Hedges will be allowed out of the country once procedures securing his release are complete.

Emirati officials have shown a video to reporters of a British national convicted for spying, saying he is a captain in MI-6.

At a news conference on Monday in Abu Dhabi, Emirati officials showed the video of Mathew Hedges, a 31-year-old doctorate student in Middle Eastern studies at Durham University.

The video, which Emirati officials did not allow journalists to record, shows Hedges describing himself as a captain in MI-6 during what appears to be a court hearing in the Gulf Arab country.

Another clip appears to show Hedges speaking to someone in an office and saying: 'It helps the research to go in an easy way.'

Then, Hedges is seen snapping his fingers and adds: 'Then it becomes MI-6.'

Emirati authorities showed the video after coming under increasing international pressure over Hedges' life sentence, handed down last week.