Ukrainian authorities say at least 12 people have been killed and dozens wounded in Russian missile and drone strikes across Ukraine , days after President Volodymyr Zelenskyy warned that Moscow was preparing a major assault.

Russia launched 656 drones and 73 missiles at Ukraine overnight, Ukraine’s air force said on Tuesday.

Kyiv Mayor Vitali Klitschko said at least four people were killed in the Ukrainian capital and 58, including two children, were wounded in the “mass enemy attack”.

“Explosions in the city. Air defence forces are working! Stay in shelters!” Klitschko had warned earlier.

In the Dnipropetrovsk region in central Ukraine, at least eight people were killed and at least 36 others, including children, were wounded in Russian attacks, Governor Oleksandr Ganzha said.

Ten people, including a child, were wounded in the city of Kharkiv in northeastern Ukraine, according to Mayor Ihor Terekhov.

Reporting from Kyiv, Al Jazeera’s Audrey Macalpine said the government had warned Ukrainians about a potential large-scale Russian attack and many had been sheltering in place.

Russia’s military said the bombardment targeted Ukraine’s military-industrial complex.

The “massive strike” using “high-precision weapons” was aimed at targets in Kyiv and the regions of Zaporizhia, Kharkiv and Dnipropetrovsk as well as energy and transport infrastructure used by the Ukrainian military in other regions, Russia’s Ministry of Defence said in a statement.

Meanwhile, a Ukrainian drone strike killed one person in Russia’s Kursk region near the border with Ukraine, Governor Alexander Khinshtein said.

Another drone attack sparked a fire at an oil refinery in the southwestern city of Krasnodar, local authorities said on Telegram.

The attacks on Ukraine came after Zelenskyy said on Friday that “we have intelligence information about Russia preparing a new massive strike” as he called on people to heed safety precautions.

“Please pay attention to air alerts. Protect your lives. Our services are working efficiently and are prepared. The air force and other defenders of our skies will be on duty 24/7, as always.”

This major Russian assault comes as United States-led peace efforts to end the war that began in February 2022 when Russia launched a full-scale invasion of neighbouring Ukraine have largely been paused as US President Donald Trump’s administration remains focused on conflicts in the Middle East.