A "massive attack" by Russian forces on Ukraine's energy infrastructure has caused power outages across the country, the state grid operator said on Saturday.
Russia has pressed on with its invasion of Ukraine in recent days despite the two countries holding US-brokered talks to end the nearly four-year-long war.
Ukrainian officials have accused Moscow of deliberately targeting energy infrastructure, causing outages that have left hundreds of thousands of people without lighting or heating in temperatures well below zero.
Ukraine's Prime Minister Denys Shmygal said Kiev had requested emergency assistance from Poland after Russia hit the Burshtynska and Dobrotvirska power plants in western Ukraine.
"Russia is carrying out another massive attack on the Ukrainian power grid facilities," grid operator Ukrenergo said on Saturday.
"Due to the damage caused by the enemy, emergency outages have been applied in most regions," it said in a statement on Telegram.
"Currently, the attack is still ongoing. Restoration work will begin as soon as the security situation allows."
Ukraine and Russia have held two rounds of US-mediated negotiations in Abu Dhabi since January.
Kiev and Moscow have agreed to a major prisoner swap but have made no breakthrough on the issue of territory, a key sticking point in negotiations.
Moscow has accused Ukraine of orchestrating the shooting of a top military intelligence general in the Russian capital on Friday, leaving him wounded. Kiev has not commented.
