LONDON - The British Foreign, Commonwealth & Development Office (FCDO) has summoned Iran's ambassador in response to a diplomatic tension following charges against three Iranian nationals under the National Security Act.

"The UK government is clear that protecting national security remains our top priority and Iran must be held accountable for its actions," the FCDO said in a statement released Monday.

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The summons follows this weekend's announcement that three Iranian nationals had been charged with engaging in activities likely to benefit a foreign intelligence service.

The three men - Mostafa Sepahvand, 39, Farhad Javadi Manesh, 44, and Shapoor Qalehali Khani Noori, 55 - appeared at the Westminster Magistrates' Court on Saturday.

According to police, they allegedly conducted activities in assisting Iran's intelligence service between Aug 14, 2024, and Feb 16, 2025. Sepahvand faces an additional charge of carrying out "surveillance, reconnaissance and open-source research" with the intent to commit serious violence against a person in the UK.

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Manesh and Noori are accused of engaging in conduct intended to enable others to carry out serious violence against a person in Britain.

In response, Iran's foreign ministry summoned the British charge d'affaires on Sunday, protesting what it described as "suspicious and unjustified" arrests of several Iranians in Britain. Iran rejected the allegations as "false" and the charges as "unrealistic."