Russia's Federal Security Service on Monday accused Ukraine's secret services of killing Darya Dugina, the daughter of a Russian ultra-nationalist, in a car bomb attack near Moscow.
Dugina, whose father Alexander Dugin is a prominent ideologue, was killed on Saturday evening when a bomb blew up the Toyota Land Cruiser that she was driving, Russian investigators said.
Ukraine, which is defending itself from what it says is an imperial-style war of conquest mounted by Russia, has denied involvement in the fatal attack.
Russia calls its actions in Ukraine a "special military operation."
Alexander Dugin, 60, has advocated violence to achieve the unification of Russian-speaking and other territories in a new Russian empire. Darya, who appeared regularly on state TV, was a strong supporter of Russia's actions in Ukraine.
In his first public statement on his daughter's death, he said Darya had been savagely killed before his own eyes by Ukraine.
"Our hearts are not simply thirsting for revenge or retribution," Dugin wrote. "We only need our victory (against Ukraine) My daughter has sacrificed her young life on the altar of victory. So please win!"
The FSB security service was quoted by Russian news agencies as saying the attack on Dugina was carried out by a Ukrainian woman born in 1979, whom it named and whose picture and personal information appeared on Russian news websites.
The websites linked her to Ukraine's security services and accused her of being a member of the Azov battalion, a unit of Ukraine's army that Russia has designated a terrorist group.
The woman and her teenage daughter had arrived in Russia in July and spent a month preparing the attack by renting an apartment in the same housing block as Dugina, the FSB was quoted as saying.
It said she had driven a Mini Cooper around Moscow which she used to spy on Dugina and for which she had three different sets of license plates to avoid detection.
She had attended an event outside Moscow on Saturday evening which Dugina and her father were also at, before carrying out a "controlled explosion" of Dugina's car. She fled Russia to Estonia in the same Mini Cooper, the FSB was quoted as saying.
There was no immediate response from Ukraine to the FSB statement.
Russian law enforcement agencies had placed the Ukrainian woman on the country's wanted list, the TASS news agency reported, with Moscow seeking her extradition from Estonia.
Estonia's foreign ministry declined to comment and there was no immediate comment from Estonia's interior ministry or police and border guard service.
President Vladimir Putin paid tribute to Dugina as a Russian patriot, while Margarita Simonyan, editor-in-chief of the Kremlin-backed RT media organization, suggested Russian agents could track the woman down in Estonia.
"Estonia, of course, will not give them away," Simonyan wrote on Telegram.
"I think we have professionals who want to admire the spires in the vicinity of Tallinn," she added, an apparent reference to a 2018 attack in England on former Russian spy Sergei Skripal which Britain said Moscow was behind.
A memorial service for Dugina would be held on Tuesday at Moscow's TV center, her father said.