The capital of Kyiv was hit on Monday by kamikaze drones, Andriy Yermak, head of the Ukrainian president's staff, wrote on the Telegram messaging app.

"Russians think it will help them," Yermak said.

Reuters was not able to independently verify the claims.

The central Shevchenkivskyi district of Ukraine's capital was rocked by blasts early on Monday for the second time in a week, with Mayor Vitalii Klitshchko saying several residential buildings were damaged.

"Rescuers are on the site," Klitshchko said on the Telegram messaging service, adding that as a result of what he said was a drone attack, a fire also broke out in a non-residential building.

There was no immediate information on casualties.

Shevchenkivskiy district, a busy hub with universities, student bars and restaurants, was hit by several explosions on Monday last week when Russia ordered the biggest aerial offensive against Ukrainian cities in retaliation for a blast on a bridge linking mainland Russia to Crimea.

Andriy Yermak, head of the Ukrainian president's staff, said the attacks were carried out with so-called suicide drones.

Ukraine has reported a spate of Russian attacks with Iranian-made Shahed-136 drones in recent weeks. Iran denies supplying the drones to Russia, while the Kremlin has not commented.

Russia denies targeting civilians in what it calls its "special military operation" in Ukraine.

Intense fighting between Russian and Ukrainian forces was taking place around two towns in the Donetsk region of eastern Ukraine, Bakhmut and Soledar, Ukrainian President Volodymyr Zelenskiy said on Sunday.

Fighting has been particularly intense this weekend in the Donetsk and Luhansk regions, which make up the larger industrial Donbas, and the strategically important Kherson province in the south. They constitute three of the four provinces Putin proclaimed as part of Russia last month, moves dismissed by Ukraine and its Western allies as illegitimate.

Bakhmut has been a target of Russia's armed forces in their slow move through the region since taking the key industrial towns of Lysychansk and Sievierodonetsk in June and July. Soledar is located just north of Bakhmut.

"The key hot spots in Donbas are Soledar and Bakhmut," Zelenskiy said in his nightly video address. "Very heavy fighting is going on there."

Russian forces shelled Ukrainian positions on several fronts on Sunday, the General Staff of Ukraine's Armed Forces said, with the targets including towns in Kharkiv, Donetsk and Kherson regions.

Ukrainian military analyst Oleh Zhdanov suggested the heaviest fighting was occuring north of Bakhmut, asserting that Ukrainian forces had repelled Russian advances on the towns of Torske and Sprine in the past 24 hours.

"(The Russians) have decided to move through Torske and Sprine," Zhdanov posted online. "Positions in those places are changing hands regularly. Our command is diverting reinforcements there, men and artillery to counter the Russian superiority in those areas."

Russia's defence ministry said on Sunday its forces had repelled efforts by Ukrainian troops to advance in the Donetsk, Kherson and Mykolaiv regions, inflicting what it described as significant losses.

Russia also said it was continuing air strikes on military and energy targets in Ukraine, using long-range precision-guided weapons.

Rybar, a pro-Russian military channel on Telegram, said Ukrainian armed forces again shelled Belgorod, a town in southern Russia that serves as a staging ground for Russian forces.

Anti-aircraft units intercepted most of the attacks, but there were two explosions near the airport. Three people were injured, it said.

Shelling by Ukrainian forces damaged the administration building in the city Donetsk, capital of the Donetsk region, the head of its Russian-backed administration said on Sunday.

"It was a direct hit, the building is seriously damaged. It is a miracle nobody was killed," said Alexei Kulemzin, surveying the wreckage, adding that all city services were still working.

There was no immediate reaction from Ukraine to the attack on Donetsk city, which was annexed by Russian-backed separatists in 2014 along with swathes of the Donbas.

Reuters was unable to independently verify the battlefield reports.

Reuters