Britain on Saturday called the execution by Iran of British-Iranian national Alireza Akbari a barbaric act and said it would not go unpunished. Earlier, the Iranian judiciary's Mizan news agency reported the execution of the former Iranian deputy defense minister who had been sentenced to death on charges of spying for Britain. "I am appalled by the execution of British-Iranian citizen Alireza Akbari in Iran," British Prime Minister Rishi Sunak said on Twitter. "This was a callous and cowardly act, carried out by a barbaric regime with no respect for the human rights of their own people." British Foreign Secretary James Cleverly also tweeted to say: "This barbaric act deserves condemnation in the strongest possible terms. This will not stand unchallenged." Iran had accused Akbari, without offering evidence, of being a spy for Britain’s MI-6 intelligence agency. It aired a highly edited video of Akbari discussing the allegations resembling others that activists have described as coerced confessions. It did not say when it happened. However, there were rumors he had been executed days ago.