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.

Air defense units intercepted 25 missiles and 365 drones, it added.

In a post on X on Tuesday, Zelensky said: 'These numbers clearly show that more protection is needed to save lives from Russian strikes. It is important to continue supporting Ukraine.'

Attacks of this scale have been occurring roughly once a week or every ten days in recent months, and there had been mounting fears in the past few days that another wave of strikes was imminent.

'Please pay attention to air raid sirens tonight,' Zelensky said earlier in his video address to the nation on Monday. 'Intelligence says Russia may be preparing a massive strike.'

This time, the attack focused on cities other than the capital, Kyiv. Damage was reported in eleven regions, Zelensky said.

Among the worst affected was the south-eastern city of Zaporizhzhia, which was struck by six drones followed by six ballistic missiles. One person was killed and nine injured after a residential high-rise building was hit, local authorities said.

Local resident Dymtro Zaiets told Reuters news agency that his family was woken by a 'very loud explosion'.

'We quickly gathered our things and ran downstairs; everything was on fire on our floor,' he said. 'There was smoke, and we took our three-month-old child and ran quickly to the underground shelter. My car is destroyed. All our windows were blown out.'

Elsewhere, at least two people were killed and 12 injured when strikes hit residential buildings and a hotel in the north-eastern Poltava region, according to governor Vitaliy Dyakivnych.

In Kherson, a civilian was killed when his house came under Russian shelling, the head of the city's military administration, Yaroslav Shanko, said.

A 75-year-old woman was injured and hospitalized after a Russian attack on the Dnipropetrovsk region, authorities said, and a 65-year-old bus driver was injured when his vehicle was hit by a drone in Sumy.

Moldova's government condemned the strike on energy infrastructure in the Odesa region, resulting in the disconnection of the Isaccea-Vulcanesti power line, which was utilized by Moldova to import electricity from Romania.

In a post on Telegram, Moldova's foreign ministry stated the attacks 'undermine regional energy security and endanger critical civilian infrastructure'.

Moscow's overnight attack occurred amidst a slowdown in the pace of the Russian advance in eastern Ukraine, with Ukrainian forces reporting minor counteroffensives in some areas.

Russia's defense ministry mentioned that its air defenses had intercepted '55 Ukrainian fixed-wing unmanned aerial vehicles' over various regions overnight.

Zelensky has cautioned that Russia will try to 'exploit the war in the Middle East to cause even greater destruction' in Ukraine.

Critical air-defense systems essential for Ukraine's defense against Russian missile attacks are being rapidly expended in the US-Israel war with Iran.

Zelensky has pointed out that peace negotiations were being 'constantly postponed', attributing it to the conflict in Iran, and emphasized that both Ukrainian and US officials had discussions over the weekend on how to bring an end to Russia's invasion.

Overall, these escalating strikes illustrate the persistent humanitarian crisis faced by civilians in Ukraine, intensifying fears of further violence and the need for urgent international support.