Russian forces have pounded Ukraine's eastern Donbas region but have failed to capture three target areas, while Moscow says Western sanctions on Russia and arms shipments to Ukraine were impeding peace negotiations.
The Russians were trying to capture the areas of Lyman in Donetsk and Sievierodonetsk and Popasna in Luhansk, the General Staff of Ukraine's Armed Forces said in a daily update on Saturday.
"Not succeeding - the fighting continues," it said.
Russian Foreign Minister Sergei Lavrov, in remarks published early on Saturday, said lifting Western sanctions on Russia was part of the peace talks, which he said were difficult but continued daily by video link.
Ukrainian President Volodymyr Zelenskiy has insisted since the Russian invasion began on February 24 that sanctions needed to be strengthened and could not be part of negotiations. He said on Friday there was a high risk the talks would end because of what he called Russia's "playbook on murdering people".
Ukraine accuses Russian troops of atrocities in areas near the capital, Kyiv, that they previously occupied. Moscow denies the claims.
Lavrov said that if the United States and other NATO countries were truly interested in resolving the Ukrainian crisis, they should stop sending weapons to Kyiv.
In Washington, US President Joe Biden's proposed $US33 billion ($A47 billion) aid package for Ukraine, including $US20 billion ($A28 billion) for weapons, has received bipartisan support. House of Representatives Speaker Nancy Pelosi said on Friday she hoped Congress would pass the package as soon as possible.
Russia calls its actions in Ukraine a "special operation" to disarm Ukraine and protect it from fascists. Ukraine and the West say the fascist allegation is baseless and the war is an unprovoked act of aggression.
The war has turned cities to rubble, killed thousands and forced five million Ukrainians to flee abroad. After failing to capture the capital, Russia is now focusing on the east and south of Ukraine.
Moscow hopes to take full control of the eastern Donbas region made up of Luhansk and Donetsk, parts of which were already controlled by Russian-backed separatists before the invasion.
Moscow on Saturday said its artillery units had struck 389 Ukrainian targets overnight. The governor of Russia's Bryansk region said air defences had prevented a Ukrainian aircraft from entering the region, and as a result shelling had hit parts of an oil terminal, Russian news agencies reported.
On the Ukrainian side, Luhansk Governor Serhiy Gaidai said the Russians were shelling all over the region "but they cannot get through our defence". He said civilians would continue to be evacuated despite the difficult situation.
Gaidai said two schools and 20 houses were destroyed by Russian attacks on Friday in the Luhansk towns of Rubizhne and Popasna.
There were also reports of attacks on places outside the Donbas, including in the southern Dnipro and Zaporizhzhia areas and the northeastern city of Kharkiv, where the regional governor said a residential area had been shelled overnight.
Britain's defence ministry said on Saturday that Russia had been forced to merge and redeploy depleted and disparate units from failed advances in northeastern Ukraine.
Reuters could not independently verify the reports on what was happening on the ground.
Zelenskiy said in his evening address on Friday that fuel shortages would end soon in Ukraine even though Russian forces had damaged a number of oil depots.
Economy Minister Yulia Svyrydenko said Ukraine's operators had secured contracts with European suppliers.