Ukrainian defenders have battled to contain Russian forces along several fronts as the US pressed China to align itself with the West against the invasion.
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A missile strike on the northeastern city of Kharkiv wounded three civilians, its governor said on Saturday, though Russia's main attacks appeared focused southeast of there in Luhansk and Donetsk.
The two provinces, swathes of which were already held by pro-Russian separatists before Russia's invasion in February, comprise the eastern industrial region of the Donbas.
Ukrainian officials reported strikes in both on Saturday, while Britain's Ministry of Defence said in a regular bulletin that Moscow was assembling reserve forces from across Russia near Ukraine.
Donetsk regional governor Pavlo Kyrylenko said on the Telegram messaging service that a Russian missile had struck Druzhkivka, a town behind the front line, and reported shelling of other population centres.
Luhansk governor Serhiy Gaidai said on Telegram that Russian forces were "firing along the entire front line", but later said a Ukrainian counter-attack had hit Russian weapons and ammunition stores and forced Moscow to halt its offensive.
On Friday, Ukraine had pleaded for more of the high-end weapons from the West that Kyiv said had thus far enabled it so slow Russia's advance.
Hours later, US President Joe Biden signed a new weapons package for Ukraine worth up to $US400 million ($A582 million), including four additional high mobility artillery rocket systems.
Ukrainian President Volodymyr Zelenskiy thanked Biden for armaments he said were priority needs.
"It is what helps us press on the enemy," he said on Twitter.
Commenting on the supply of weapons, the Russian embassy in Washington said the US wanted to "prolong the conflict at all costs" and compensate for Ukrainian military losses.
On Saturday US Secretary of State Antony Blinken, urging the international community to condemn Russian aggression, said he had raised concerns with his Chinese counterpart Wang Yi over Beijing's alignment with Moscow, during talks that lasted over five hours.
Blinken spoke to journalists from the Indonesian island of Bali after a gathering on Friday of G20 foreign ministers.
Russia's Sergei Lavrov had walked out of a meeting there, denouncing the West for its "frenzied criticism".
Australian Associated Press
