Britain says Tehran's "weakened and isolated regime" will be held responsible after it executed U.K.-Iranian dual national Alireza Akbari in what London called a "callous and cowardly” act.
"Our message to that regime is clear: The world is watching you, and you will be held to account, particularly by the brave Iranian people, so many of whom you are oppressing and killing," Foreign Secretary James Cleverly said on January 16.
"We are witnessing the vengeful actions of a weakened and isolated regime, obsessed with suppressing its own people, debilitated by its own fear of losing power, and wrecking its international reputation," he said in comments to the British Parliament.
Cleverly did not comment on specific actions or sanctions Britain might plan, but he said that "we do not limit ourselves to the steps that I have already announced."
Akbari, 61, a former Iranian deputy defense minister, was sentenced to death for spying for Britain in what critics called a "political" decision, raising condemnation from Western governments and rights groups.
German Foreign Minister Annalena Baerbock on January 16 joined the condemnations and summoned Iran's ambassador to Berlin for the second time in a week over a recent surge in executions.
SEE ALSO: Germany Summons Iran Envoy Over Latest ExecutionThe Iranian judiciary's Mizan news agency announced Akbari's execution on January 14 but did not say when it took place. Some reports indicated it may have been several days before.
The Mizan report said Akbari was executed after being "sentenced to death on charges of corruption on Earth and extensive action against the country's internal and external security through espionage for the British government's intelligence service."
The report also alleged that Akbari had received payments amounting to more than $2 million for spying, charges Akbari and Britain denied.
Britain and the United States had called on Iran to not carry out the sentence.
Iran does not recognize dual nationality for its citizens.
London has placed sanctions on Iran's prosecutor-general, Mohammad Jafar Montazeri, but has so far resisted pressure from Iranian opposition exiles, activists, and the British Parliament to list Iran's Islamic Revolutionary Guards Corps (IRGC) as a terrorist group.
SEE ALSO: Thousands Demand EU Blacklisting Of Iran's Revolutionary GuardsA spokesman for British Prime Minister Rishi Sunak's told reporters that "we are reviewing further action with our international partners."
Earlier, Sunak called the execution a "callous and cowardly act, carried out by a barbaric regime."
The British government appears to be treading cautiously due to the fact that other dual nationals are still being held by Tehran. London also is involved in difficult negotiation between Tehran and other world powers to revive a landmark nuclear pact.