Mostafa Sepahvand, 39, Farhad Javadi Manesh, 44, and Shapoor Qalehali Khani Noori, 55, appeared via video link from a high-security prison in south London.
The three Iranian nationals have been charged with engaging in conduct likely to assist a foreign intelligence service between 14 August 2024 and 16 February 2025.
Sepahvand has also been charged with engaging in conduct, namely surveillance, reconnaissance and open-source research, between 14 August 2024 and 16 February 2025, intending to commit acts, namely serious violence against a person in the United Kingdom.
Manesh and Noori have also been charged with engaging in conduct, namely surveillance and reconnaissance, with the intention that acts, namely serious violence against a person in the United Kingdom, would be committed by others.
The charges include collecting information and planning to commit acts of violence on British soil.
Their targets are allegedly staff members of Iran International.