Kiev’s energy company said on Sunday planned blackouts had been introduced in the Ukrainian capital as Russia repeatedly targeted the country’s power grid.

According to the Ukrainian Presidency, more than a million Ukrainian homes have lost power after the latest Russian strikes, with at least a third of the country’s power plants destroyed before the winter.

Moscow announced a new incursion on Sunday, saying it had destroyed a warehouse in central Ukraine that was storing over 100,000 tons of aviation fuel.

Ukrainian President Volodymyr Zelenskyy on Saturday night denounced “heinous attacks on critical objects” by Russia after fresh attacks on energy facilities and power outages were reported across the country, including in western Ukraine — far from the frontlines.

National energy operator Ukrenergo introduced “stabilization shutdowns” in Kyiv on Sunday to “prevent accidents,” energy company DTEK said in a statement on its website.

The blackouts began at 11:13 a.m. (0813 GMT), with consumers in Kyiv divided into three groups who “will be disconnected for a period of time,” DTEK said.

It added that the power outages should last “no more than four hours” but could be longer “due to the extent of the damage to the power system”.

DTEK again urged residents to be “sparing” with electricity and urged businesses to limit the use of outdoor lighting.

In the southern Ukrainian city of Kryvyi Rig, Deputy Mayor Sergiy Miliutin battled emergencies and power outages in his underground bunker, which was used as a venue for a children’s martial arts competition.

“I’ve gotten to a point where I’m just surviving on my ride. You have to stay calm and conserve your energy. No one knows how long this will all last,” he told AFP.

The intensification of Russian attacks on Ukraine, particularly on power plants, came after the bridge linking the annexed Crimea peninsula to mainland Russia was partially destroyed by an explosion earlier this month.

The incident was seen as another major setback for Moscow forces fighting to contain a Ukrainian counter-offensive in the south and east of the country.

Russian Defense Minister Sergei Shoigu held phone calls with his French, Turkish and British counterparts to discuss Ukraine.

In all three calls, Shoigu expressed “concern about possible provocations by Ukraine using a ‘dirty bomb,'” the Russian Defense Ministry said.

Ukraine reported three dead in a night Russian artillery attack in the Toretsk region, a governor of the eastern Donetsk region said.

In Russia itself, two lines of defense have been built in the Kursk region near the border with Ukraine to repel a possible attack, a local governor said on Sunday.

The move came a day after the governor of the neighboring Belgorod region, which also borders Ukraine, said construction of defense installations had started in parts of the region.

The governor, Vyacheslav Gladkov, also reported the deaths of two civilians in strikes in his region on Saturday, adding that 15,000 people were left without power.

Ukraine’s secret service, the SBU, launched a new charge of alleged cooperation, saying it had arrested two officials at Ukrainian aircraft engine maker Motor Sich on suspicion of cooperation with Russia.

The SBU said management of the company’s plant in Ukraine’s southern Zaporizhia region – part of which is controlled by Russian forces – “acted in collusion” with Russia’s state-run defense conglomerate Rostec.

“The suspects established a transnational channel for the illegal delivery of wholesale batches of Ukrainian aircraft engines to the aggressor country,” the SBU said, specifying that Russia used them to manufacture and repair combat helicopters.

The blackouts and deadly strikes came as pro-Moscow officials in southern Ukraine’s Kherson region, which Russia is said to have annexed, on Saturday urged residents to leave “immediately” amid a “tense situation” at the front lines.

Kherson, the capital of the region, was the first to fall to Moscow forces, and its recapture would be a great asset in Ukraine’s counteroffensive.

A Moscow-based Kherson official, Kirill Stremousov, told Russia’s Interfax news agency on Saturday that around 25,000 people had left the city of Kherson for the left bank of the Dnieper River.

Ukraine has described the deportation of residents of Kherson as “deportations”.