Russia's Federal Security Service (FSB) on Monday held Ukrainian authorities responsible for killing Darya Dugina, a Russian journalist.
Ukrainian citizen Natalya Vovk executed the murder premeditated by the Ukrainian special service, the FSB said in a statement.
Vovk arrived in Russia on July 23 with her daughter Sofia Shaban, the security agency said.
"On the day of the murder, Vovk and Shaban were at the literary and musical festival Tradition, where Dugina was present as an honorary guest.
"After committing a controlled explosion of a Toyota Land Cruiser Prado car, driven by Dugina, on August 21, Vovk, together with her daughter, left through the Pskov region for Estonia," the statement added.
The mother-daughter duo rented an apartment in Moscow in the same building where Dugina lived to watch her closely, the security agency said.
Vovk used a Mini Cooper car to stalk Dugina, FSB added.
The car's number plates were changed several times, when entering Russia, in Moscow and when leaving Ukraine, it further said.
Dugina was killed in a car explosion on the outskirts of Moscow late Saturday.
Initial reports said she died instantly, adding that her father, Aleksandr Dugin, who switched cars last minute, was the original target.