Ukraine warned on Friday that peace talks with Moscow were in danger of collapse and said Russia was pounding areas in the east as US lawmakers vowed to swiftly approve a massive new weapons package for Kyiv.
Russian forces have turned their focus toward Ukraine's east and south after failing to capture the capital in a nine-week assault that has turned cities to rubble, killed thousands and forced 5 million Ukrainians to flee abroad.
Moscow captured the city of Kherson in Ukraine's south and its forces have mostly occupied the eastern port city of Mariupol, where United Nations efforts are under way to evacuate civilians and fighters holed up in a large steel plant.
Ukraine and Russia have not held face-to-face peace talks since March 29, and the atmosphere has soured over Ukrainian allegations that Russian troops carried out atrocities as they withdrew from areas near Kyiv. Moscow has denied the claims. The two sides have since held talks by video link.
In comments to journalists in Poland, which has taken in nearly 3 million Ukrainian refugees, President Volodymyr Zelenskiy expressed pessimism over the prospect of continued negotiations with Russia, blaming public anger with what he said were Russian atrocities.
"The risks that the talks will end are high because of what they (the Russians) have left behind them, the impression that they have a playbook on murdering people," Interfax quoted Zelenskiy as telling Polish journalists.
Moscow says it launched its invasion in part over concerns that Ukraine might join the US-led NATO military alliance. Russia's foreign minister, Sergei Lavrov, said that Ukraine would have been given security guarantees from U.N. Security Council countries if it had been "honest" in negotiations.
"We got stuck because of their inconsistency, because of their desire to play games every time and - as far as I can guess - because of instructions they get from Washington, London and other capitals not to speed up the negotiating process," Lavrov said in an interview reported by Russian news agencies.
Both the United States and Britain have voiced support for Ukraine in the talks but say it is vital to continue arming Kyiv. President Joe Biden on Thursday asked the US Congress for $33 billion in new aid, including over $20 billion in weapons.
The funding has received bipartisan congressional support and House of Representatives Speaker Nancy Pelosi said she hoped to pass the package "as soon as possible".
Putin calls Moscow's actions a "special military operation" to disarm Ukraine, defend Russian-speaking people from persecution and prevent the United States from using the country to threaten Russia.
Ukraine dismisses Putin's claims of persecution and says it is fighting an imperial-style land grab aimed at fully capturing two eastern Ukrainian provinces, Donetsk and Luhansk, which are collectively known as the Donbas.
Russia was pounding Donetsk's whole front line with rockets, artillery, mortar bombs and aircraft in part to stop Ukrainian troops from regrouping, Ukrainian officials said.
Ukraine's military said Russia was preparing for offensives in the areas of Lyman in Donetsk and Severodonetsk and Popasna in Luhansk. In the south, Russia was "continuing to regroup, increase fire effectiveness and improve position," it added.Russia's defence ministry said its forces had struck Ukrainian weapons storage sites, platoon strongholds, artillery positions and drones. Russia said earlier a diesel submarine in the Black Sea had struck military targets with Kalibr cruise missiles, the first reported such strikes from a submarine.
Russia also said its high precision long-range missiles had destroyed the production facilities of a rocket plant in Kyiv. Ukraine says that attack Thursday struck a residential building, injuring civilians and killing a producer with U.S.-backed broadcaster Radio Free Europe/Radio Liberty.
The body of the producer, Vira Hyrych, was found in the building's rubble, RFE/RL said.
"She was going to bed when a Russian ballistic missile hit her apartment in central Kyiv," Ukrainian Foreign Ministry spokesperson Oleg Nikolenko said.
A US official confirmed the Kyiv attack had targeted military production, without saying if the target was destroyed.
Ukraine has acknowledged losing control of some eastern towns and villages, but says Moscow's gains have come at a heavy cost to a Russian force already worn down from its earlier defeat near the capital.
"We have serious losses but the Russians' losses are much, much bigger ... They have colossal losses," Ukrainian presidential adviser Oleksiy Arestovych said, without elaborating.
Western officials said Russia had been suffering fewer casualties after narrowing the scale of its invasion but numbers were still "quite high", while the British defence ministry said Russian gains had been limited and came at "significant cost".
The bloodiest fighting and worst humanitarian catastrophe of the war have been in Mariupol, reduced to a wasteland by two months of Russian bombardment and siege. Ukraine says 100,000 civilians remain in the city.
In parts of Mariupol now held by Russian troops, emergency workers were gathering up bodies from the streets. Residents among the blasted ruins recounted the horror they had survived.
"We were hungry, the child was crying when the Grad (multiple rocket launcher) shells were striking near the house. We were thinking, this is it, the end. It can't be described," Viktoria Nikolayeva, 54, who survived the battle with her family in a basement, told Reuters, weeping.
UN Secretary-General Antonio Guterres said during a visit to Kyiv on Thursday that intense discussion were under way to evacuate Ukrainians from Mariupol's Azovstal steel works.
One Ukrainian fighter holed up there expressed belief that he and other fighters would be able to save the injured and other soldiers at the plant and they would reach safety. Previous efforts to evacuate the plant have failed."I really believe that all the defenders of Mariupol - the troops that remained here, the wounded and those alive - that we will be able to save the lives of these heroes," Captain Sviatoslav Palamar said.