Kyiv residents should be prepared to leave the city if there is a total loss of power, mayor Vitaliy Klitschko has said.

In recent weeks, millions of Ukrainians have intermittently been left without electricity and water as Russian air strikes target vital infrastructure.

Rolling power cuts are also in place to avoid overloads and allow for repairs.

Some 40% of Ukraine’s energy system has been damaged or destroyed by Russian attacks on power plants and lines.

President Volodymyr Zelensky has warned that Russia could be “concentrating forces and means for a possible repetition of mass attacks on our infrastructure, energy in the first instance”.

The Geneva Conventions, which outline humanitarian standards for treatment in war, state that attacks should not be carried out against “civilian objects”.

Speaking on Ukrainian television, Mayor Klitschko branded Russia’s targeting of infrastructure as “terrorism” and “genocide”.

Russian President Vladimir Putin “doesn’t need us Ukrainians. He needs territory, he needs Ukraine without us”, the former heavyweight boxer said.

“That’s why everything that is happening now [strikes on infrastructure] is genocide. His task is for us to die, to freeze, or to make us flee our land so that he can have it.”

Another official in the capital Kyiv has warned that, in the case of a total blackout, water supply and sewerage would also stop working.

In winter in Kyiv, the average temperature is below freezing and drops even further at night.

Mr Klitschko said that while authorities are doing “everything” to keep the lights on and water flowing, he was ensuring preparations were in place for different scenarios.

Kyiv’s three million residents should make arrangements to stay with friends or relatives who live in the suburbs who still have water and power, so that they have a plan in the “worst case” scenario if the supply to Kyiv is lost, the 51 year old said.

He added that the authorities were stocking up on fuel, food and water, and residents should do the same. At least 1,000 heating shelters are being set up across the city where people will be able to get warm in an emergency.

Kyiv’s Director of Security, Roman Tkachuk, echoed the mayor’s comments in a post on messaging app Telegram.

He stressed that city officials were making plans but that “there are no reasons to talk about the evacuation at the moment”.

Residents in Kyiv have said that they know that power could be lost and supplies could become scarce.

Dmytro, a 30-year-old father-of-two told the BBC he had already made plans to leave Kyiv in case things got worse. He has stocked up on fuel, bought generators and will move his family to his grandparents’ home on the outskirts of Kyiv.

He said he began making the plans after “authorities announced that they were going to open heating points” two weeks ago.

“I understood from that there will eventually be no electricity,” he added.

Another resident, Anastasia, 36, said she would remain in the city even if power was lost.

“Our defenders sleep on the ground, so we will manage to stay in our apartment even without heating,” she said.

Russian-installed authorities have reported power and water loss in occupied Kherson, blaming a Ukrainian strike on nearby power lines and a key dam.

They urged residents to “remain calm” and said they would “quickly” resolve the situation.

However, the head of the Ukrainian regional administration blamed Russia for the power outage.

Some of the power outage was caused by damage to the nearby hydroelectric Kakhovka dam after it was hit by a missile, according to Russian media, However, Ukraine has not commented on the reports, which cannot be independently verified.

In recent weeks Ukraine has warned that Russian forces intend to blow up the dam, causing devastating flooding for hundreds of thousands of people in the surrounding area.

Kherson – which lies downriver of the dam – fell to Russia within the first days of the war but as Ukrainian forces advance they have their sights set on retaking it.

Russia is suffering “heavy losses” as it carries out “fierce” attacks in Ukraine’s eastern Donetsk region, President Zelensky said in his nightly television address.

The Insider, a Russia-focused, independent media outlet, reported that in four days, 300 members of a brigade of Russian marines were killed, wounded or missing in the Pavlivka area.

Posts on pro-Russian Telegram channels have been drawing attention to the brigade’s reportedly dire situation.