Nazanin Zaghari-Ratcliffe, a British-Iranian woman who has been in prison in Tehran for more than two years on sedition charges, has been released for three days, her husband said Thursday.

"Nazanin was released from Evin prison on furlough this morning. Initially the release is for three days -- her lawyer is hopeful this can be extended," Richard Ratcliffe said in a statement.

Ratcliffe said his wife was currently with her parents and their four-year-old daughter Gabriella in Damavand, a resort near Tehran.

"This was a very happy surprise after a number of false dawns recently, which had been increasingly unsettling," he said.

"Our thanks to all those involved in making this possible in Tehran and London, and to the new Foreign Secretary (Jeremy Hunt) for all his recent efforts and considerations."

Zaghari-Ratcliffe, who works for the Thomson Reuters Foundation -- the media organisation's philanthropic arm -- was arrested at Tehran airport in April 2016.

She is serving a five-year jail sentence for alleged sedition -- a charge she has always denied.

Ratcliffe and his supporters have held multiple protests and vigils in London to ask for her release in the past two years.

The Free Nazanin campaign said that after several weeks of bureaucracy over her possible temporary furlough, Zaghari-Ratcliffe was told earlier on Thursday that she had 10 minutes to get ready because she was being released.

She was not allowed to call her family and had to borrow a phone from someone outside the prison to call her brother, who lives in Tehran, to pick her up.

She then called her husband and the British embassy and travelled to join the rest of her Iranian family in Damavand.

"I cried so much. I felt so overwhelmed," she was quoted as saying in the statement released by The Free Nazanin campaign, which is run by her husband.

Zaghari-Ratcliffe was told she must return to prison on Sunday and the two conditions of her release are that she not give any media interviews or visit the grounds of any foreign embassy.

Bail for her temporary release was set at 1 billion rials ($23,840, 20,590 euros), with her family's home in Tehran used as collateral, according to the campaign.