At least six people have been killed and more than 30 are feared trapped after Russian rockets destroyed a five-storey residential building in Ukraine's Donetsk region, the Interior Ministry said on Sunday.
Regional governor Pavlo Kyrylenko said on Telegram that the strike took place on Saturday evening in the town of Chasiv Yar. He said six people were confirmed killed and five were wounded.
The ministry confirmed the death toll and said at least 35 people were trapped in the rubble. It said rescuers had established contact with at least two people.
Mr Kyrylenko said the town of about 12,000 was hit by Uragan rockets, which are fired from lorry-borne systems. Chasiv Yar is about 20 kilometres south-east of Kramatorsk, a city that is expected to be a major target for Russian forces as they move west.
Along with Luhansk, Donetsk is one of two provinces that make up the Donbas region, where separatist rebels have fought Ukrainian forces since 2014. Last week, Russia captured the city of Lysychansk, the last major stronghold of Ukrainian resistance in Luhansk.
Mr Kyrylenko said there were Russian attacks on other parts of the Donetsk region on Saturday, including a missile strike on Druzhkivka, a town behind the front line.
Serhiy Gaidai, the governor of Luhansk, said Russian forces were "firing along the entire front line" on Saturday, though a subsequent Ukrainian counter-attack forced Moscow to halt its offensive.
Ukraine President Volodymyr Zelenskyy said the Russian army had deliberately fired on civilians.
"It fired precisely at the residential sector – absolutely deliberately, purposefully, at ordinary houses and civilian objects," Mr Zelenskyy said.
Russia, which says it is conducting a "special military operation" to demilitarise Ukraine, denies attacking civilians.
Russia's Ministry of Defence said its forces hit two "bases of foreign mercenaries deployed near Kharkiv", about 250km north-west of Luhansk.
Ministry spokesman Igor Konashenkov also said troops had destroyed ammunition depots in the Mykolayiv, Dnipropetrovsk and Donetsk regions.
Russian-backed forces in the territory of the self-proclaimed Donetsk People's Republic said three people died and 17 were wounded there in the past 24 hours as Ukrainian forces shelled 10 locations.
Alexei Kulemzin, mayor of Donetsk, wrote on Telegram that two women had died as a result of shelling in the city's Kirovskyi district.
Meanwhile, Mr Zelenskyy said he had dismissed several of Kyiv's senior envoys abroad as part of "normal diplomatic practice". He said he would appoint new ambassadors to Germany, India, the Czech Republic, Norway and Hungary.
The president has urged his diplomats to drum up international support and advanced weapons to slow Russia's advance.
US President Joe Biden signed a weapons package for Ukraine on Friday worth up to $400 million, including four more high-mobility artillery rocket systems (HIMARS).
But Ukraine suffered a diplomatic setback on Saturday when Canada said it would return a repaired turbine that Russia's state-controlled Gazprom used to supply natural gas to Germany. Ukraine had argued that a return would violate sanctions on Russia.
US Secretary of State Antony Blinken, urging the international community to join forces to condemn Russian aggression, told journalists he had raised concerns with his Chinese counterpart, Wang Yi, over Beijing's alignment with Moscow.
The pair held more five hours of talks on the sidelines of the G20 meeting of foreign ministers on the Indonesian island of Bali. On Friday, Russian Foreign Minister Sergey Lavrov walked out of a meeting there, denouncing the West for "frenzied criticism".
The Chinese Ministry of Foreign Affairs said, without giving details, that Mr Wang and Mr Blinken had discussed "the Ukraine issue".
It also quoted Mr Wang as saying that Sino-American relations were in danger of being further led "astray", with many people believing that "the United States is suffering from an increasingly serious bout of 'Chinaphobia'".
Shortly before the Russia invaded Ukraine on February 24, Beijing and Moscow announced a "no limits" partnership, although US officials have said they have not seen China evade US-led sanctions on Russia or provide it with military equipment.
With reporting from agencies.