Three Iranian men charged with offences under the National Security Act arrived in the UK by "irregular means", including small boats and a lorry, before claiming asylum, Sky News understands.
The trio appeared at Westminster Magistrates Court on Saturday, charged with engaging in conduct likely to assist a foreign intelligence service between 14 August 2024 and 16 February 2025, following an investigation by counter-terror police.
The foreign state to which the charges relate is Iran, police said.
Mostafa Sepahvand, 39, Farhad Javadi Manesh, 44, and Shapoor Qalehali Khani Noori, 55, are accused of targeting journalists working for Iran International, an independent media organisation based in London.
Sepahvand, of St John's Wood, London, is charged with "surveillance, reconnaissance and open-source research" with the intention of "committing serious violence against a person in the UK", according to a police statement.
Meanwhile, Manesh, of Kensal Rise, London, and Noori, of Ealing, London, are charged with "engaging in conduct, namely surveillance and reconnaissance, with the intention that acts, namely serious violence against a person in the UK, would be committed by others".
They were remanded in custody to appear at the Old Bailey on 6 June.
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Commander Dominic Murphy, from the Metropolitan Police's Counter Terrorism Command, described the charges as "extremely serious".
"Since the men were arrested two weeks ago, detectives have been working around the clock and we have worked closely with colleagues in the Crown Prosecution Service to reach this point," he said.
"Now that these men have been charged, I would urge people not to speculate about this case, so that the criminal justice process can run its course."
A fourth Iranian national aged 31 who was arrested was released with no further action on Thursday.
In a separate unrelated probe, counter-terror officers arrested five Iranian men, aged between 29 and 46, during raids across various locations in Greater Manchester, London, and Swindon earlier this month. Four remain in custody and one has been released on bail with conditions.
Home Secretary Yvette Cooper said in response to the charges: "Iran must be held to account for its actions.
"We must also strengthen our powers to protect our national security as we will not tolerate growing state threats on our soil."
She said the government will next week publish its independent barrister-led report commissioned into the UK "counter-terrorism framework to modern-day state threats".
Last October, MI5 director general Ken McCallum said the UK intelligence agency had responded to 20 "potentially lethal" Iran-backed plots since 2022, warning of the risk of an "increase or broadening of Iranian state aggression in the UK".
(c) Sky News 2025: Three Iranian men charged under National Security Act arrived in UK by small boat and lorry
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