Russia’s top counterintelligence agency Monday blamed the Ukrainian spy service for the car bomb explosion that killed the daughter of a leading Russian nationalist ideologue, both of whom have been staunch supporters of President Vladimir Putin’s invasion of Ukraine.

Russia’s Federal Security Service [FSB], the main KGB successor agency, said that the Saturday night killing of Daria Dugina, the 29-year-old daughter of Alexander Dugin, was “prepared and perpetrated by the Ukrainian special services.”

There has been no claim of responsibility. On Sunday, Ukraine’s presidential adviser Mykhailo Podolyak denied any Ukrainian involvement in the car bombing.

But in a statement, the FSB accused a Ukrainian citizen, Natalya Vovk, of carrying out the car bombing and then fleeing with her 12-year-old daughter from Russia to Estonia.

The Russian security agency said Vovk and her daughter arrived in Russia in July and rented an apartment in the building where Dugina lived to shadow her. It said the two Ukrainians were at a nationalist festival, which the elder Dugin and his daughter attended, just before the car bombing.

The FSB said that Vovk and her daughter left for Estonia, using a different vehicle license plate on their way out of the country.

Russian media have speculated that the car bombing quite possibly was intended to hit Dugin, a philosopher, writer and political theorist whom some in the West have described as “Putin’s brain.”

Russian media reports cited witnesses who said the Toyota Land Cruiser SUV that exploded belonged to Dugin and that he had decided at the last minute to travel in another vehicle as he left the festival.

Even before the FSB statement blaming Ukraine, Denis Pushilin, head of the Russia-backed separatist “Donetsk People’s Republic” in Ukraine’s east, on Sunday claimed the blast was the responsibility of “terrorists of the Ukrainian regime, trying to kill Alexander Dugin.”

In his writings and appearances on Russian state television, Dugin has helped popularize the concept of “Novorossiya,” or “New Russia,” that Russia used to justify the 2014 seizure of Ukraine’s Crimean Peninsula and its support of separatist rebels in eastern Ukraine for the last eight years leading up to Putin’s invasion of Ukraine six months ago.

An ultranationalist, Dugin is a prominent proponent of the “Russian world” concept espoused by Putin, a spiritual and political ideology that emphasizes traditional values, restoration of Russia’s power and the unity of all ethnic Russians throughout the world.

Dugin, who has been slapped with U.S. and European Union sanctions, has ridiculed Western liberal values. His daughter has expressed similar views while appearing as a commentator on the nationalist TV channel Tsargrad, where Dugin had served as chief editor.

Dugina was sanctioned by the United States in March for her work as chief editor of United World International, a website that the U.S. described as a disinformation source.

In an appearance on Russian television Thursday, Dugina said, “People in the West are living in a dream, in a dream given to them by global hegemony.” She called the United States “a zombie society,” but said that Americans who opposed Russia couldn’t find it on a map.

Some material in this report came from The Associated Press.