MOSCOW (Reuters) - Russia’s FSB security service planned and organized the murder of a Georgian man in Berlin last summer, a killing that triggered diplomatic expulsions from Germany and Moscow, the investigative website Bellingcat said on Monday.

Citing mobile phone metadata and a months-long investigation conducted with Der Spiegel and The Insider, Bellingcat published information it said showed the assassin was trained and supplied with false identity papers by the FSB, the successor agency to the Soviet-era KGB.

The FSB did not immediately respond to a request for comment. Russia has denied involvement in the killing.

The Russian-Georgian victim, known as Zelimkhan Khangoshvili, was a former Chechen rebel who had fought against Russian forces. He was shot dead on Aug. 23 in a Berlin park.

Surveillance footage showed his killer cycled up to him but that Khangoshvili had managed to push him over. He then tried to flee, but his killer pursued him and shot him at least twice, German prosecutors have said.

His suspected killer, a man traveling on a Russian passport, is in German custody.

Germany expelled two Russian diplomats in December over what it said was Moscow’s refusal to cooperate in the investigation. Russia responded by expelling two German diplomats.

Russian President Vladimir Putin said in December that Khangoshvili was himself a killer who took part in bloody acts on Russian soil.

Putin called Khangoshvili “a cruel and blood-thirsty person,” saying the murdered man had fought on the side of anti-Moscow separatists in Russia’s mainly Muslim north Caucasus region.

Tensions between Russia and Western countries including Germany, which is heavily reliant on Russian gas and oil, are already high after the 2018 poisoning of a former Russian spy, Sergei Skripal, and his daughter on British soil.