A “sophisticated” UK-based spy ring passed secrets to Russia for nearly three years, a court has heard.

Bulgarian nationals Katrin Ivanova, 33, Vanya Gaberova, 30, and Tihomir Ivanov Ivanchev, 39, allegedly carried out surveillance on individuals and places of interest to Russia.

The spying activities allegedly included locations in London, Vienna, Valencia, Montenegro and Stuttgart, jurors have heard.

Court artist sketch of Bulgarian national Vanya Gaberova (Elizabeth Cook/PA)

Opening the trial on Thursday, Alison Morgan KC said: “This case is about espionage activity.

“Between 2020 and 2023 these three defendants together with a number of other people spied for the benefit of Russia.

“Over a period of nearly three years they sought to gather information for the benefit of Russia, an enemy of the UK, information about various targets, both people and physical locations. Information of particular interest to the Russian state.

“Their activity caused obvious and inevitable prejudice to the safety and interests of the United Kingdom.”

Ms Morgan said the defendants were “sophisticated in their methodology” as they allegedly conducted surveillance.

They allegedly manufactured and used fake identities and deployed “advanced technology” to acquire information.

The prosecutor said they obtained imagery and compiled detailed reports on their targets for which they were paid “significant amounts of money”.

Ms Morgan said: “They all knew why they were being tasked to conduct their operations. Their activity was being undertaken for the direct or indirect benefit of Russia.”

The spy ring included two more defendants, Orlin Roussev and Biser Dzhambazov, who have pleaded guilty to espionage charges, the court was told.

Court sketch of Bulgarian national Tihomir Ivanov Ivanchev (Elizabeth Cook/PA)

The defendants have denied a charge of conspiracy to spy between August 30 2020 and February 8 2023.

Ivanova has denied a second charge of possession of false identity documents with improper intention under section 4 of the Identity Documents Act 2010.

At the time of the alleged offences, Ivanchev was living in Acton, west London, Ivanova was living in Harrow, north-west London, and Gaberova in Euston, north London.

The Old Bailey trial is expected to go on until February next year.