Ukrainian authorities issued air raid alerts in much of the country on Tuesday, after Kyiv's air force confirmed the takeoff of Russian bombers from western Russia.
"Takeoff of several Tu-95MS from the Engels airfield has been recorded," Ukraine's air force said on Telegram, estimating that missiles could enter Ukrainian air space around 4:00 am (0100 GMT).
UN nuclear watchdog head Rafael Grossi is to visit Russia's Kursk nuclear plant on Tuesday to "independently assess" events following Ukraine's unprecedented cross-border offensive into the Russian region.
US President Joe Biden and Indian Prime Minister Narendra Modi on Monday discussed the Russia-Ukraine war following Modi's visit to Ukraine.
Poland said that a drone had likely entered its airspace early on Monday morning during a Russian bombardment of Ukraine, adding that the object may have landed on Polish territory and that searches were underway.
The United States voiced outrage Monday at the Russian assault on Ukraine's power grid and vowed sustained support for Kyiv.
Kyiv urged allies to allow long-range strikes in order to "accelerate the end of Russian terror" following Moscow's massive strike on Ukraine on Monday.
