The United Arab Emirates says it has pardoned and released British academic Matthew Hedges, who had been sentenced to life in prison for spying.

Key points: Matthew Hedges was arrested in the UAE in May and convicted of espionage last week

Matthew Hedges was arrested in the UAE in May and convicted of espionage last week The UAE maintains he is guilty of espionage but pardoned him along with 784 other prisoners

The UAE maintains he is guilty of espionage but pardoned him along with 784 other prisoners Mr Hedges' wife says the news of his pardon "brought her back to life"

The announcement came after authorities showed journalists a video of Mr Hedges, who has been detained for more than six months, purportedly saying he was a captain in British intelligence.

Emirati authorities had come under increasing international pressure over Mr Hedges' life sentence, handed down last week, and a news conference was hastily called to announce his pardon in the UAE capital, Abu Dhabi.

An Emirati official giving the media conference declined to take any questions from journalists but said the pardon was "in response to the letter from the family of Mr Hedges requesting clemency and in consideration of the historic relationship and close ties between the United Arab Emirates and the United Kingdom".

Authorities said Mr Hedges would be allowed out of the country once procedures securing his release are complete, but it is not yet known when that will be.

A clip viewed by media appears to show Hedges admitting he is a captain in MI6. ( Supplied )

Mr Hedges' wife said she had been "brought back to life" by the news he had received a pardon after being arrested back in May.

"I can't wait to have him back," Daniela Tejada told BBC on Monday, when word of the pardon reached Britain.

"In my heart, I know that he isn't a spy."

Mr Hedges' wife said in her heart she knows he is not a spy. ( Supplied )

Ms Tejada has said he was kept in solitary confinement for more than five months and the evidence presented against him consisted of notes from his dissertation research.

British Foreign Secretary Jeremy Hunt, who lobbied intensively for Mr Hedges' release, called the news "fantastic".

Loading

In a video shown during the announcement of his pardon, Mr Hedges, a 31-year-old doctorate student in Middle Eastern studies at Durham University, is seen describing himself as a captain in MI6 during what appears to be a court hearing in the Gulf Arab country.

Emirati officials did not allow journalists to record the video, which was sometimes inaudible and shown with subtitles that could not be independently verified, but Mr Hedges did appear to say he approached sources as a doctoral student.

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

Then Mr Hedges is seen snapping his fingers and adds: "Then it becomes MI6."

"During the investigation it emerged that Mr Hedges has been using two different identities to gather information from his targets," the UAE spokesman said.

"In one, he was Matthew Hedges the 'PhD researcher', in another one he was Matthew Hedges the businessman.

"He was part-time PhD researcher, part-time businessman but he was 100 per cent a full-time secret service operative."

The UAE maintains Mr Hedges was in the country "to steal UAE sensitive national security secrets" for his "masters".

According to the announcement, UAE President Khalifa bin Zayed al-Nahyan issued the clemency for Mr Hedges, along with 784 others.

AP/Reuters