In a statement published by Iran's Intelligence Ministry, Alireza Akbari was described as "one of the most important infiltrators of the country's sensitive and strategic centres".

Akbari was arrested in 2019.

"Our priority is securing his immediate release and we have reiterated our request for urgent consular access," a UK Foreign Office spokesperson said.

Akbari's death sentence has been upheld by Iran's Supreme Court, Nournews, an Iranian news agency affiliated to the country's top security agency, reported.

(Reporting by Dubai NewsroomEditing by Frank Jack Daniel and Peter Graff)