A Russian attack overnight on Ternopil in western Ukraine killed 25 people and wounded at least 66 others, including 16 children, were injured, Ukrainian authorities said on Wednesday.

Russia fired 476 strike and decoy drones, as well as 48 missiles of various types, at Ukrainian targets overnight, Ukraine’s air force said.

Russia's defence ministry said on Wednesday that Moscow had launched"massive" overnight strikes on targets in western Ukraine in response to what it called "terrorist attacks".

Moscow has been intensifying its daily drone and missile barrages in recent months, targeting Ukraine's energy infrastructure and hitting a number of civilian sites ahead of winter.

“Every brazen attack against ordinary life indicates that the pressure on Russia (to stop the war) is insufficient,” Ukrainian President Volodymyr Zelensky wrote on the messaging app Telegram.

At least 46 people were wounded in an overnight attack on Kharkiv, the third such attack on the eastern region in three days.

Strikes in Kharkiv damaged more than 10 apartment buildings, a school, a supermarket and an ambulance substation, among other buildings, authorities said.

Two children aged nine and 13 were among those wounded, police said, adding"doctors diagnosed the children with acute stress reactions".

State media Suspilne said rescuers and police evacuated 48 people, including three children, from the smoke-filled entrance of a high-rise building, citing regional emergency services spokesperson Yevgen Vasylenko.

On Wednesday morning, the whole of Ukraine was under an air raid alert, with authorities in several western cities issuing warnings to their residents.

"The enemy is attacking western Ukraine with drones. Do not ignore the alert! Stay in shelters," Lviv Mayor Andriy Sadovy wrote on Telegram.

"Residents of Lviv region, please do not publish any photos, videos, addresses. Keep the informational silence," he said.

Ukraine's energy ministry said Russian attacks had resulted in emergency power outages in a number of regions.

In October, Moscow launched its biggest bombing campaign against Ukrainian gas facilities since the start of the 2022 invasion.

Facing another gruelling winter and no sign of peace talks, Ukrainian President Volodymyr Zelensky is on a European tour trying to garner support for his army and energy infrastructure.

Exhausted and outnumbered Ukrainian troops are struggling to fend off the larger Russian army as it advances on the front in eastern Ukraine, claiming two more villages on Tuesday.