Ukrainian presidential adviser Mykhailo Podolyak said on Friday that Kyiv had nothing to do with Friday's attack by gunmen at a Moscow concert hall.
The United States had warned Russia on March 8 that "extremists" had imminent plans for an attack in Moscow.
Kyiv almost never publicly claims responsibility for attacks inside Russia or on Russian-controlled territory in Ukraine.
Russia has also blamed Ukrainian spies for bombings that killed the daughter of a nationalist writer near Moscow, and a pro-war blogger in St Petersburg.