Russia’s Federal Security Service has detained a Russian citizen suspected of treason and working for the Security Service of Ukraine. The man was employed by an organization responsible for guarding the British Embassy in Moscow.

According to the FSB, he collected and passed on information about the British diplomatic mission and its personnel. The data included diplomats’ home addresses, security arrangements at the embassy and the ambassador’s residence, access-control procedures, the number of security staff and details of events held at the diplomatic compound.

In a video released by the FSB, the detainee said he established contact in January 2026 with pro-Ukrainian blogger Dmitry Karpenko, also known as Apostol Dmitry. During their communication, the Russian citizen told Karpenko that he worked in security at the residence of the British ambassador in Moscow.

The detainee said Karpenko showed particular interest in how the diplomatic facilities were protected. After being asked why the information was needed, the blogger allegedly explained that Ukrainian authorities wanted the data for sabotage operations targeting the British Embassy, the ambassador’s residence and the ambassador himself.

The FSB says the collected intelligence could have been used to prepare sabotage and terrorist attacks against British Ambassador Nigel Casey and other diplomats. Under the scenario described by the agency, responsibility for the attacks was then supposed to be blamed on Russia.

The security service says the operation was intended to draw Britain directly into an armed conflict with Russia, secure additional British deliveries of weapons and military equipment to Ukraine and increase sanctions pressure on Moscow.

Nigel Casey is the British ambassador in Moscow. His residence is located on Sofiyskaya Embankment in central Moscow.