At least five people have been killed in Russian strikes across Ukraine, after a massive overnight aerial bombardment targeted several regions across the country.

A 61-year-old woman was killed when a drone hit an electric train in Kharkiv early on Tuesday, authorities said, while other deaths were reported in Zaporizhzhia, Kherson and Poltava.

Officials said the attacks were among the worst in ten days, and came hours after Ukrainian President Volodymyr Zelensky had warned of a forthcoming "massive strike" in his nightly address.

Russian strikes targeting energy infrastructure also disconnected Moldova's key power link with Europe, President Maia Sandu said, warning the situation remained "fragile".

Sirens wailed across Ukraine on Monday night as Russia launched a barrage of missiles and drones at the country. Seven ballistic missiles, 23 cruise missiles, four air-launched guided missiles and 392 drones were used in the attack, the Ukrainian Air Force said in a statement on Telegram.