(CNN) Ukrainian forces have unleashed the biggest attack on the occupied Donetsk region since 2014, according to a Russia-installed official, in the wake of heavy fighting in the east of the country.
Donetsk has been held by Russian-backed separatists for eight years and it is one of four Ukrainian regions that Moscow attempted to annex in October, in violation of international law.
"At exactly 7 a.m. the (Ukrainians) subjected the center of Donetsk (city) to the most massive strike since 2014," the Moscow-appointed mayor, Aleksey Kulemzin, posted on Telegram.
"Forty rockets from BM-21 'Grad' MLRS were fired at civilians in our city," he said Thursday, adding that a key intersection in Donetsk city center had come under fire.
Kulemzin shared photographs on Telegram of damage to residential and commercial buildings and a cathedral.
There have been no immediate reports of casualties, according to Russian state media.
CNN cannot independently confirm Kulemzin's claims.
The war in Ukraine ramped up further south as Russia also launched fresh assaults on Kherson overnight, after a wave of fatal shelling in the region earlier this week. Ukrainian forces retook control of the city last month in one of the most significant breakthroughs of the war to date.
The city was hit 86 times with "artillery, MLRS, tanks, mortars and UAVs," in the past 24 hours, according to the regional head of the Kherson military administration.
Ongoing shelling from Moscow has killed at least two people on Thursday and wounded another three people, Yaroslav Yanushevych said on Telegram.
"One of (the victims) was a volunteer, a member of the rapid response team of the international organization. During the shelling, they were on the street, they were fatally wounded by fragments of enemy shells," he added.
Yanushevych added that three people were killed and 13 injured, including a 8-year-old boy, on Wednesday.
The ramped-up strikes in Donetsk and Kherson took place against the backdrop of a harsh winter season in Ukraine inflamed by wide-ranging power outages, caused by Russia's targeting of critical infrastructure, and a grinding war of attrition on the battlefield.
The strikes in Kherson left the city "completely disconnected" from power supplies, according to the regional head of the Kherson military administration, Yanushevych.
"The enemy hit a critical infrastructure facility. Shell fragments damaged residential buildings and the place where the medical aid and humanitarian aid distribution point is located," Yanushevych later said in a Telegram video on Thursday.
Meanwhile, further west Kyiv received machinery and generators from the United States to help strengthen the Ukrainian capital's power infrastructure amid the widespread energy deficits.
Kyiv's mayor, Vitali Klitschko, said the city "received machinery and generators from the U.S. Government to operate boiler houses and heat supply stations."
The Energy Security Project, run by USAID, delivered four excavators and over 130 generators, Klitschko said on Telegram. All equipment was free of charge.
This week, the Kremlin also appeared to rebuff Ukrainian President Volodymyr Zelensky's peace solution that involved asking Russia to start withdrawing troops from Ukraine this Christmas -- as the war approaches the 10-month mark.
"The Ukrainian side needs to take into account the realities that have developed over all this time," Kremlin spokesperson Dmitry Peskov said Tuesday in response to Zelensky's three-step proposal.
"And these realities indicate that the Russian Federation has new subjects," he said, referring to four areas Russia has claimed to have annexed, Donetsk, Kherson, Luhansk and Zaporizhzhia.
"Without taking these new realities into account, any progress is impossible," Peskov added.