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Mr Putin ordered his Defence Minister Sergei Shoigu to scrap plans to storm the Azovstal steel plant after being told there were more than 2,000 Ukrainian fighters still holed up in its tunnels.
Ramzan Kadyrov, the Chechen leader whose forces are fighting in Ukraine, had predicted on Thursday the Azovstal plant would be under Russian control “before lunchtime, or after lunch”, completing the capture of Mariupol.
But Mr Putin, who described the rest of Mariupol as having been liberated by Russian troops, said in a televised exchange with Mr Shoigu that “there is no need to climb into these catacombs and crawl underground” at the plant.
“I consider the proposed storming of the industrial zone unnecessary,” he said. "Block off this industrial area so that a fly cannot not pass through."
The seizure of Mariupol would be Russia’s most significant strategic and symbolic victory of the eight-week war in Ukraine, giving it a land corridor between annexed Crimea and occupied territories in the eastern Donbas region.
Western officials say the protracted struggle for the port, which has prompted hundreds of thousands of civilians to flee, has tied up Russia’s troops and equipment and bogged down its wider offensive in Ukraine.
Ukrainian President Volodymyr Zelenskyy said about a thousand civilians were sheltering behind troops defending Mariupol. The two sides blamed each other for faltering efforts to establish humanitarian escape routes.
“Our warriors have hundreds of wounded,” said Mr Zelenskyy, who said the situation in Mariupol was deteriorating. “Protecting ordinary civilians with their backs, they lose their lives.”
Britain’s Defence Ministry said in a regular intelligence update that Russian forces were advancing on Kramatorsk, another city, from staging areas in the Donbas as it focuses its offensive on the south and east.
It said the speed and force of Russian attacks could intensify as it aims for a military and propaganda triumph by the time of the May 9 Victory Day parade in Moscow.
Mr Zelenskyy likewise said the situation in the south and east “remains as severe as possible” as Russia seeks “something they can feed their propagandists”.
Ukraine said Russia had lost 21,000 troops as of Thursday, as well as 830 tanks, 170 aircraft, 150 helicopters and scores of other vehicles and pieces of equipment.
Moscow has acknowledged significant casualties and is believed by western officials to have turned to mercenaries from the Wagner Group, a private company widely thought to have close links to the Kremlin.
One European official was quoted by The Guardian as saying between 10,000 and 20,000 fighters had been drafted in from Libya, Syria and other theatres where Wagner has a presence.
These troops were being used as infantry forces and did not bring heavy equipment or vehicles with them, the official said.
Russia, meanwhile, insists the invasion it calls a special military operation is running as planned despite setbacks such as its failure to overpower Kyiv and the loss of its Black Sea flagship Moskva.
The offensive will end when the aims of demilitarising and “de-Nazifying” Ukraine, eliminating threats to Russia and protecting the largely Russian-speaking population of the Donbas are achieved, foreign ministry official Alexey Polishchuk told Tass news agency.
Mr Zelenskyy said more than 900 towns in Ukraine had been recaptured from Russian forces, with local government and police restored to their posts in many of those settlements.
But he told people returning to their homes to watch out for mines and tripwires left behind by Russian forces and to wait for inspections by the Ukrainian authorities.