ABU DHABI/DUBAI - The United Arab Emirates on Monday pardoned and released a British academic jailed for life on spying charges, granting a request for clemency after showing a video of him purportedly confessing to membership of the UK's MI6 intelligence service.

The case has strained ties between the long-time allies, leading London to issue a forceful diplomatic response after last week's verdict was handed down, with a warning that it could hurt relations.

The UAE president issued the pardon as part of a mass clemency of more than 700 prisoners to mark the country's National Day, according to a statement on state news agency WAM.

The pardon was effective immediately and Matthew Hedges, a 31-year-old doctoral student at Durham University held for more than six months, will be allowed to leave the country "once formalities are completed," the statement said.

A UAE official later said Hedges lad been freed.

Britain's Foreign Secretary Jeremy Hunt welcomed the move, which he called "fantastic news".

"Although we didn't agree with charges we are grateful to UAE government for resolving issue speedily."

Hunt said it was also a "bittersweet moment" because he was thinking about innocent people still detained in Iran, the arch-foe of Abu Dhabi. "Justice won't be truly done until they too are safely home," he said.

Hedge's wife Daniela Tejada said his family was "elated" over the news.