A Russian attack overnight on Ternopil in western Ukraine killed nine people and wounded dozens of others, Ukrainian President Volodymyr Zelensky said Wednesday.

"In Ternopil, residential nine-storey buildings were hit... as of now, dozens of people are known to have been injured and, sadly, nine people have died," he said on social media.

At least 36 people were also wounded by Russian strikes in Ukraine's Kharkiv, authorities said Wednesday, the third such attack on the eastern region in three days.

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.

Kharkiv police said at least 36 people were wounded in the latest overnight attack, which damaged more than 10 apartment buildings, a school, a supermarket and an ambulance substation, among other buildings.

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"Residents of Lviv region, please do not publish any photos, videos, addresses.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.