Ukraine reported clashes with Russian troops on fronts in the east and south, with six civilians killed in one rocket attack, as the United States sought to marshal international support in opposing Russia's invasion.
At least six people have been killed and more than 30 are feared trapped after Russian Uragan rockets hit a five-storey apartment block in Ukraine's Donetsk region, collapsing the building, the region's governor said.
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 gathering in the area of the village of Bilohorivka, about 50 km (30 miles) east of Sloviansk, from where they were shelling the surrounding settlements and carrying out air strikes.
Russia's Tass news agency cited pro-Russian separatists as saying Ukrainian forces had fired an artillery barrage into residential districts of the city of Donetsk.
Reuters could not independently verify battlefield accounts.
U.S. 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.
Ukrainian President Volodymyr Zelenskiy dismissed several of Kyiv's senior envoys abroad, including the outspoken ambassador to Germany.
G20 foreign ministers called for an end to the war and grain blockade in Ukraine, as Russia's top diplomat walked out of a meeting and denounced the West for "frenzied criticism" and squandering a chance to tackle global economic problems.
President Vladimir Putin said continued sanctions against Russia could lead to "catastrophic" energy price rises for European consumers.
President Zelenskiy said on Saturday that he had dismissed several of Kyiv's senior envoys abroad, including the country's outspoken ambassador to Germany.
Zelenskiy announced the sacking of Ukraine's ambassadors to Germany, India, the Czech Republic, Norway and Hungary and said new candidates were being readied for the positions.
"This rotation is a normal part of diplomatic practice," he said in a statement.
It is not clear if the envoys would be assigned new positions.
Zelenskiy has urged his diplomats to drum up international support and military aid for Ukraine as it tries to fend off Russia's Feb. 24 invasion.
Kyiv's relations with Germany, which is heavily reliant on Russian energy supplies and also Europe's biggest economy, are particularly sensitive.
Andriy Melnyk, who was appointed by Zelenskiy's predecessor as ambassador to Germany in late 2014, is well known among politicians and diplomats in Berlin.
The 46-year-old regularly engages in outspoken social media exchanges and has branded politicians and intellectuals who oppose arming Ukraine to fight the Russian invasion as appeasers.
He once accused German Chancellor Olaf Scholz of behaving like an "offended liver sausage" when Scholz did not immediately accept an invitation by Zelenskiy to visit Kyiv.
Kyiv and Berlin are currently at odds over a German-made turbine undergoing maintenance in Canada.