Russian forces pounded Ukraine’s power plants and heating systems on Saturday with some of the heaviest missile strikes in weeks, Ukrainian officials said, as Moscow pressed ahead with an aerial campaign to bring misery to the country’s civilians even as it loses ground on the battlefield.

In a sign that Moscow’s forces in the south were coming under pressure, occupation officials in the southern province of Kherson told residents of the region’s capital city on Saturday to “immediately” leave because of the threat of an attack by Ukrainian forces.

Ukraine endures bitter winters, making its people vulnerable at this time of year to energy disruptions. Ukrainian officials confirmed missile strikes in at least half a dozen regions on Saturday, with the country’s foreign minister, Dmytro Kuleba, saying that the barrage was “aimed at critical civilian infrastructure”.

The state power company said that while it was trying to restore services, it had imposed energy restrictions ina string of regions, including the capital, Kyiv. The damage from Saturday’s attacks, the company, Ukrenergo, said in an online post, was “comparable or may exceed” anything it had seen in the last two weeks.

Not since the first days after the invasion in February has the bombing been so widespread and intense.