Air raid sirens wailed across Ukraine, including the capital Kyiv, on Saturday, officials said, a day after Russia carried out a massive missile strike on critical infrastructure.
"Please go to the shelters!" Kyiv city's military administration said on Telegram.
Belarusian social media account Hajun, which monitors military activity in Belarus, said several Russian warplanes had been spotted flying above Belarus to the north of Ukraine.
Reuters could not independently verify that information.
This is a developing story.