Ukraine’s security service said it has detained an alleged Russian agent in Kiev suspected of overseeing separatist forces in eastern Ukraine.

The SBU security service identified the suspect as Ukrainian citizen Andrei Nikolayevich, whose last name was only given as the initial K. He is alleged to be a “freelance representative” for the GRU Russian military intelligence agency in the separatist Donetsk People’s Republic (DPR), helping it create an intelligence unit, and other units.

“Citizen K. served as one of the so-called DPR’s ‘curators’ through the [GRU] from 2014-2020,” the SBU said in a statement Tuesday.

In 2014, Russia annexed Crimea from Ukraine and a war that has killed more than 13,000 people broke out between Ukrainian forces and pro-Russian rebels in the eastern Ukrainian region called the Donbass.

Western countries accuse Russia of providing troops, equipment and funding to the separatists and have sanctioned Moscow over its role in the conflict.

Intercepted phone calls published on Tuesday by the SBU showed suspect K’s alleged conversations with two Russian suspects in the murder trial over the downing of Malaysia Airlines Flight 17. A number of high-ranking Russian officials, including the head of Russia’s FSB security agency Alexander Bortnikov and former Kremlin aide Vladislav Surkov, were named in the conversations.

The Dutch-led investigation accuses three Russian nationals and one Ukrainian of playing key roles in transporting and launching the missile system that brought down MH17 in July 2014 and killed 298 mostly Dutch citizens. 

Several former fighters have told the investigation that the FSB and the GRU were involved in the daily management of the DPR. 

The SBU accused the suspect K. of creating a terrorist group and said it plans to indict him in the near future. The charges carry a sentence of up to 15 years in prison.