Russia bombarded 118 Ukrainian towns and villages in 24 hours, more than on any other day this year, says Ukrainian Interior Minister Ihor Klymenko.
He said 10 of Ukraine’s 27 regions had come under attack and the onslaught had caused deaths and injuries.
Many of the communities hit were near the front lines in the east and south.
Russia has for weeks trained much of its military firepower on Avdiivka, a strategically significant town in the eastern region of Donetsk.
“[Avdiivka] is being erased, shattered. There have been more than 40 massive shelling attacks against the territorial community in the past day,” said local leader Vitaliy Barabash.
He said two civilians had been killed and warned that Russia was building up to a third wave in its offensive. Ukraine says Russia has been pouring reinforcements into the area in a bid to encircle and capture the town.
Twenty attacks in the Avdiivka area alone were repelled on Tuesday, Ukraine’s armed forces general staff said.
Russia has also ramped up attacks on the town of Kupyansk in the north-eastern Kharkiv region and sought to stop Ukrainian forces from recapturing territory around Bakhmut.
There were also attacks away from the front lines, on a block of flats, shops and a pharmacy in the southern city of Nikopol on the bank of the Dnipro river, and in Kremenchuk, where a disused oil refinery was set on fire by a Russian drone.
The refinery, in the central region of Poltava, has been targeted several times by Russia and officials said it had come under attack throughout the early hours of Wednesday.
The Kremenchuk refinery was the biggest in Ukraine until Russian attacks put it out of action a few weeks into the full-scale invasion.
Ukraine’s counter-offensive has so far made little headway in recapturing land occupied by Russian forces in the south and east, prompting fears of Western fatigue with the war.
Ukrainian President Volodymyr Zelensky has admitted the slow progress, repeatedly urging Kyiv’s allies to urgently provide more advanced weapon, and also stay united.
On Wednesday, Ukraine’s chief military commander Zaluzhny warned that the war was now moving to a “positional” or static stage.
In a column for the Economist, he said this would benefit Moscow by “allowing it to rebuild its military power”.
Despite heavy losses, Russia still had “superiority in weapons, equipment, missiles and ammunition”, Mr Zaluzhny warned, calling on Ukraine’s allies to deliver warplanes and drones, as well as modern electronic warfare and mine-breaching technology, among other things.
One of the Ukrainian leader’s closest allies, Italian Prime Minister Giorgia Meloni, addressed the issue of fatigue during a hoax call from two Russian pranksters, widely known for targeting Kremlin opponents.
“I see there is a lot of fatigue, if I have to say the truth, from all the sides,” she is heard to tell the pair, Vovan and Lexus. “We’re near the moment in which everybody understands that we need a way out.”
“The counter-offensive of Ukraine is maybe not going as they were expecting. It is going, but it didn’t change, I mean, the destiny of the conflict.”
US President Joe Biden’s administration has asked Congress to approve a $106bn package for both Ukraine and Israel. US Defense Secretary Lloyd Austin warned this week: “I can guarantee that without our support [Russia’s Vladimir] Putin will be successful.”
President Volodymyr Zelensky told Ukrainians in an overnight address on Tuesday that “we live in a world that gets used to success too quickly”.
He reserved particular praise for the military’s success in reducing Russia’s control over the Black Sea: “The more protection we have along our coastline and in our sea, the more protection there is in the world.”
Recent Ukrainian attacks have hit the headquarters of Russia’s Black Sea fleet prompting most of its ships to leave occupied Crimea.
Kyiv has tried to create an export corridor safe for civilian vessels to carry grain along Ukraine’s Black Sea coast, via Romanian waters and on to the Turkish coast.
Although at least 700,000 metric tonnes of grain have evaded Russian bombardment in recent months, Ukrainian officials said war planes had dropped “explosive objects” on the expected paths of civilian ships. “However, the functioning of the navigational corridor continues under the aegis of the defence forces,” said Ukraine’s southern operational command.
Russian Defence Minister Sergei Shoigu said on Wednesday that Ukraine was losing the war despite supplies of new weapons from Nato.
He said that Ukraine was taking heavy losses as it tried to push into Russian-held areas of Zaporizhzhia, Kherson and Donetsk and “demoralisation of personnel is growing”. He also claimed Russian units were advancing.
Mr Shoigu provided no evidence to back his claims.
Russian President Vladimir Putin launched a full-scale invasion of Ukraine in February 2022.
