Russia is attempting to overwhelm Ukrainian forces with barrages of artillery and air strikes as the battle for control of the Donbas region continues, UK intelligence says.
Despite recent advances, Russian troops have so far failed to capture the key strategic city of Severodonetsk amid intense street fighting that has resulted in a high number of casualties on both sides.
In an updated intelligence briefing on Saturday, the Ministry of Defence said Russia was "massing fires with its artillery and air capabilities" in an attempt to overwhelm Ukrainian defences.
It also said that Russia is deploying 1960s era Kh-22 anti-ship missiles against land targets, which could cause "significant collateral damage and civilian casualties".
These 5.5 tonne missiles are "inefficient" and "highly inaccurate" as they were primarily designed to destroy aircraft carriers using a nuclear warhead, the MoD said.
Moscow is resorting to more unconventional attack methods because it is running low on more precise modern missile systems and its fighter jets continue to be thwarted by Ukrainian anti-air capabilities, it said.
The government in Kyiv has pleaded with western countries for faster deliveries of modern battlefield weapons, saying it is massively outgunned by better-armed Russian troops.
The war in the east, where Russia is focussing its attention, is now primarily an artillery battle in which Kyiv is severely outgunned, Ukrainian officials say.
"This is an artillery war now," Vadym Skibitsky, Ukraine's deputy head of military intelligence, told Britain's The Guardian newspaper.
"Everything now depends on what (the West) gives us. Ukraine has one artillery piece to 10 to 15 Russian artillery pieces."
Ukraine has said the tide of events could be turned only if Washington and others fulfil promises to send more and better weaponry, including rocket systems.
It comes as Ukrainian President Volodymyr Zelenskyy said Russia was trying to "break every town in the Donbas".
"Severodonetsk, Lysychansk, Bakhmut, Sloviansk, many, many others," he said in his nightly address. "All these ruins were once happy towns."
Mr Zelenskyy's adviser Oleksiy Arestovych estimated the Russian army is losing on average five to six times as many fighters as the Ukrainian side.
Asked in a social media interview whether that suggested the Ukrainian army had lost up to 10,000 fighters in the first 100 days of the war, Mr Arestovych said, "Yes, something like that.”
Weapons experts from France are helping their Ukrainian counterparts collect evidence of possible Russian war crimes in the northern region of Chernihiv, Ukraine's prosecutor general said. Russia denies targeting civilians.
US Defence Secretary Lloyd Austin on Saturday reinforced Washington's commitment to the region in light of Russia's actions.
"Russia’s invasion of Ukraine is what happens when oppressors trample the rules that protect us all," Mr Austin told an Asian security forum in Singapore. "It's a preview of a possible world of chaos and turmoil that none of us would want to live in."
Mr Zelenskyy is expected to give a virtual address to the conference from 0800 GMT.
