President Volodymyr Zelenskyy said earlier this week that around 4,000 buildings in the capital Kyiv were still without heating and most of the city was cut off from electricity after Russian strikes.
The EU said on Friday it was sending hundreds more generators to Ukraine to help provide electricity to key facilities as Russian strikes have cut power and heating during freezing winter temperatures.
"Over one million Ukrainians are without electricity, water and heating in freezing temperatures following relentless Russian strikes on energy infrastructure," the European Commission said in a statement.
"The European Commission is today deploying 447 emergency generators worth €3.7 million from EU strategic reserves to restore power to hospitals, shelters and critical services."
"Russia's continued attacks on Ukraine's energy infrastructure are deliberately depriving civilians of heat, light and basic services in the middle of harsh winter," said European Union crisis management commissioner Hadja Lahbib.
Lahbib said the shipment of 447 generators was on its way, and will add to the 9,500 that the EU has already supplied to the country.
Brussels said they would be used to provide power to "hospitals, shelters and critical services."
Ukrainian President Volodymyr Zelensky said last week that he was declaring a "state of emergency" in the energy sector, after relentless Russian strikes on heat and electricity supplies as freezing winter temperatures have dipped to -20C.
On Wednesday he said that around 4,000 buildings in the capital Kyiv were still without heating and most of the city was cut off from electricity after Russian strikes earlier in the week.
"As of this morning, about 4,000 buildings in Kyiv are still without heat and nearly 60 percent of the capital is without electricity," Zelenskyy said, after Russia pounded Ukraine's energy grid between Monday and Tuesday.
Russia has repeatedly hit Ukrainian energy infrastructure throughout the nearly four-year war, but Kyiv says this winter has been the toughest yet, with hundreds of Russian drones and missiles overwhelming air defences during particularly fierce frosts.
More than 1,000 Ukrainians have been taken to hospital with frostbite and hypothermia over the past 30 days, the health ministry said, adding that the situation could "become threatening if temperatures drop or weather conditions worsen."
Germany called the Russian winter airstrikes against energy infrastructure "war crimes."
Russia has been pounding Ukraine's energy system since the start of its invasion, in what Kyiv says is an attempt to sap morale and weaken Ukrainians' resistance.
The Kremlin says it only targets Ukrainian military facilities and has blamed the continuation of the war on Kyiv for refusing to accept its peace demands.
The Russian defence ministry said on Tuesday it had carried out strikes on facilities that support Ukraine's military.
Meanwhile, US negotiators led by Steve Witkoff met with Russian President Vladimir Putin in Moscow for marathon overnight talks on ending Russia's full-scale invasion that lasted well into Friday morning.
Kremlin diplomatic adviser Yuri Ushakov told reporters that their discussions had been "useful in every respect," as Moscow insisted that its territorial demands must be answered to reach a peace deal.
Zelenskyy said later on Friday that two days of trilateral meetings involving the US, Ukraine and Russia are due to begin on Friday in the United Arab Emirates.
"Russians have to be ready for compromises because, you know, everybody has to be ready, not only Ukraine, and this is important for us," he said.