Iranian state media published a video on Thursday in which British-Iranian national Alireza Akbari, sentenced to death for spying, said he played a role in the 2020 assassination of the country's top nuclear scientist.  In a separate audio recording broadcast by BBC Persian on Wednesday, Akbari said he was tortured in detention over months to confess to crimes he had not committed.  Iran sentenced the former deputy defense minister, who holds dual Iranian-British citizenship, to death on charges of spying for Britain, Iranian state media reported on Wednesday.  Britain described the death sentence as politically motivated and called for his immediate release. British officials did not immediately comment about the video clips aired by Iran's state media.  "They wanted to know about high-ranking officials depending on the major developments ... for example he (the British agent) asked me whether Fakhrizadeh could be involved in such and such projects and I said why not," Akbari said in one of the video clips.  Scientist Mohsen Fakhrizadeh, killed in a 2020 attack outside Tehran, was widely seen by Western intelligence as the mastermind of clandestine Iranian efforts to develop nuclear weapons. Tehran denied that.  Iran’s state media often airs purported confessions by suspects in politically charged cases.  In the audio recording broadcast by BBC Persian, Akbari said he was forced to confess to crimes he had not committed.  "I was interrogated and tortured for over 3,500 hours in 10 months. All of that were recorded on camera ...By using the force of gun and making death threats they made me confess to false and baseless claims," Akbari said in the audio message.  Akbari was a close ally of Ali Shamkhani, secretary of Iran’s Supreme National Security Council who served as defense minister from 1997 to 2005 when Akbari was his deputy.  "He was one of the most important agents of the British intelligence service in Iran who had access to some very sensitive centers in the country," Iran's Intelligence Ministry said. "Akbari had fully, knowingly provided information to the enemy's spy service."