A US think tank says Russia's large-scale attack on the Ukrainian capital of Kyiv on Wednesday was "likely in retaliation" for the Ukrainian drone strikes on Moscow and the Pskov region.
The Institute for the Study of War released the analysis on Wednesday. Kyiv city officials say the day's attack, which killed two people and injured three, was the largest since this past spring.
Russia has faced a series of drone attacks recently. On Tuesday and Wednesday, six Russian regions were targeted.
Russia's state-run media reported that a drone attack on a military airport in the northwestern region of Pskov damaged four Ilyushin-76 transport planes.
Russia's defense ministry said on Thursday that a drone attack was attempted outside Moscow, but its air defense systems deterred it. The ministry said Ukraine was responsible.
The British defense ministry said also on Thursday that Russia experienced 25 separate drone attacks during August.
The ministry says Russia is "likely rethinking its air defence posture" to better deal with these attacks.