A British woman of Iranian descent incarcerated in Iran on sedition charges since 2016 was granted a three-day furlough on Thursday to see her young daughter and other relatives, a break in a bitter dispute between Britain and Iran.

Word that the prisoner, Nazanin Zaghari-Ratcliffe, had been allowed to temporarily leave Tehran’s Evin Prison was welcomed by her family and supporters including Britain’s new foreign secretary, Jeremy Hunt, who called it “really good news.”

The imprisonment of Ms. Zaghari-Ratcliffe, 39, a program coordinator for the Thompson Reuters Foundation, an educational charity, has been a major source of friction in Britain-Iran relations. She is one of several British citizens of Iranian descent thought to be incarcerated in Iran.

The Free Nazanin Campaign, an advocacy organization based in Britain that announced she had been released temporarily, said in a statement that Ms. Zaghari-Ratcliffe was staying with family members in the historic city of Damavand, near Tehran, and that she was “overwhelmed.”