Russia’s Federal Security Service (FSB) has said it intercepted a Ukrainian saboteur group that was planning a terrorist attack against two nuclear power plants in the country ahead of May 9, when Russians celebrate the Soviet Union’s victory over Nazi Germany.

The suspects were aiming to destroy more than 30 pylons of high-voltage lines linked to the nuclear power plants, the FSB announced in a statement on Thursday.

Before being detained, the Ukrainian agents were able to blow up one transmission tower and mine four others on power lines leading to the Leningrad nuclear plant near St. Petersburg, according to the statement.

They also placed improvised explosive devices at pylons connected to the Kalinin nuclear power plant in Tver Region, 350km northwest of Moscow, it added.

Ukraine’s Foreign Intelligence Service, which according to the FSB was behind the plot, hoped that the sabotage “would cause the shutdown of nuclear reactors, disruption of routine operations of the nuclear power plants, and deliver serious economic and reputational damage to Russia,” the statement claimed.Read more Another Ukrainian terrorist plot foiled – FSB

The FSB said two Ukrainian citizens were arrested, while another, who is believed to be in Belgium, was placed on the wanted list.

The three men were allegedly recruited by Ukrainian intelligence in September last year and underwent training at camps in the Kiev and Nikolaev Regions of Ukraine. They illegally crossed into Russia in Pskov Region from Belarus, which they had entered from Poland, the agency said.

Russian operatives discovered caches prepared by the suspects, containing 36.5kg of C-4 plastic explosives, 61 foreign-made electric detonators, 38 electronic timers and two Makarov pistols with ammunition, the statement read.

Two Russian citizens were also detained on suspicion of providing means of communication and vehicles with fake license plates to the Ukrainian saboteurs, the FSB added.