BERLIN (Reuters) - German federal prosecutors believe Russian intelligence was involved in the August killing of a Georgian citizen and will therefore take over the investigation from local authorities, a legal source said on Tuesday.

Such a step could fan already heightened tensions between Germany - and other Western countries - and Russia, following the poisoning of a former Russian spy, Sergei Skripal, and his daughter on British soil last year.

Zelimkhan Khangoshvili, 40, who had previously fought alongside anti-Moscow separatists in the Russian region of Chechnya, was shot twice in the head in a central Berlin park in August as he was heading to a mosque.

“We have evidence that a foreign intelligence agency was behind it and therefore the case is going to be taken over by the federal prosecutor this week,” said the legal source, who asked not to be named as he was not authorized to speak to media.

A suspect was detained shortly after the killing and the news magazine Der Spiegel has reported that his passport number linked him to Russian security services.

Berlin prosecutors, who have so far presided over the case, said the suspect had been caught as he tried to dispose of the presumptive murder weapon in the nearby Spree River, along with a bicycle he had been riding.

The Russian government did not immediately comment on the development. But the Kremlin said in August that it categorically rejected the idea that there was any link between the killing and the Russian government.

Russia fought major campaigns in 1994-96 and 1999-2000 against separatists in Chechnya, situated in the Caucasus Mountains on Russia’s border with Georgia. Many anti-Moscow fighters from those wars now live in exile and are at odds with the current pro-Russian authorities in Chechnya.