Fighting raged northwest of Kyiv on Saturday, with the bulk of Russian ground forces 25 km (16 miles) from the centre of the Ukrainian capital, while several other cities were encircled and under heavy shelling, the UK Defence Ministry said.
Ukraine's Deputy Prime Minister Iryna Vereshchuk said she hoped that several humanitarian corridors would open on Saturday for thousands of residents in the bombarded cities, including from the besieged port city of Mariupol to Zaporizhzhia.
"I hope that the day will go well, all the planned routes will be open and Russia will fulfill its obligations to guarantee the ceasefire regime," Vereshchuk said in a video address after repeated evacuation efforts this week failed.
1,582 Civilians Killed in Mariupol
At least 1,582 civilians in the southeastern city of Mariupol have been killed as a result of Russian shelling and a 12-day blockade, the city council said in an online statement on Friday. It was not possible to verify casualty figures.
Air raid sirens blared across most Ukrainian cities on Saturday morning urging people to seek shelters, local media reported, after President Volodymyr Zelenskiy said the war had reached a "strategic turning point".
Russian forces appeared to be regrouping, possibly for a fresh offensive which could target the capital Kyiv in a few days, Britain's defence ministry said on Friday. In a Saturday update, it said fighting northwest of the capital continued and the cities of Kharkiv, Chernihiv, Sumy and Mariupol remained encircled under heavy Russian shelling.
Efforts to isolate Russia economically have stepped up, with the United States imposing new sanctions on senior Kremlin officials and Russian oligarchs and the European Union set to strip Russia of its privileged trade status on Saturday.
With the Russian assault in its third week, Zelenskiy, who has rallied his people with a series of addresses from the capital Kyiv, said Ukraine had "already reached a strategic turning point".
"It is impossible to say how many days we still have (ahead of us) to free Ukrainian land. But we can say we will do it," he said. "We are already moving towards our goal, our victory."
The United States on Friday imposed sanctions on Russian billionaire Viktor Vekselberg, three family members of President Vladimir Putin's spokesperson and lawmakers in the latest punishment for Russia's Feb. 24 invasion.
"Treasury continues to hold Russian officials to account for enabling Putin's unjustified and unprovoked war," Treasury Secretary Janet Yellen said.
Russian forces kept up their bombardment of cities across the country on Friday in the biggest assault on a European country since World War Two. Satellite images showed them firing artillery as they advanced on Kyiv.
The fighting has created more than 2 million refugees, and thousands of Ukrainians are trapped in besieged cities.
As hundreds sheltered in Kharkiv metro stations, Nastya, a young girl lying on a makeshift bed on the floor of a train carriage, said she had been there for over a week, unable to move around much and ill with a virus.
"I'm scared for my home, for the homes of my friends, very scared for the whole country, and scared for myself of course," she said.
Putin calls the invasion a "special operation" to disarm Ukraine and unseat leaders it calls neo-Nazis. Ukraine and Western allies call this a baseless pretext for a war of choice that has raised fears of wider conflict in Europe.
The governor of the Kharkiv region on the Russian border, said a psychiatric hospital had been hit, and the mayor of the city of Kharkiv said about 50 schools there had been destroyed.
In the southern city of Mariupol, the city council said at least 1,582 civilians had been killed by Russian shelling and a 12-day blockade that has left hundreds of thousands trapped with no food, water, heat or power.
Moscow denies targeting civilians.
Situation Critical, Says Ukraine
Russia's defence ministry said the Black Sea port was surrounded, while Vereshchuk said Russian shelling prevented people from leaving along a humanitarian corridor on Friday.
"The situation is critical," Ukrainian interior ministry adviser Vadym Denysenko said.
Western countries meanwhile took more economic steps to try to force Putin to end his assault.
President Joe Biden, who this week banned U.S. imports of Russian oil, said the G7 industrial powers would revoke Russia's "most favoured nation" trade status. He also banned U.S. imports of Russian seafood, alcohol and diamonds.
European Commission President Ursula von der Leyen said the EU would on Saturday suspend Moscow's privileged trade and economic treatment, crack down on its use of crypto-assets, and ban the import of iron and steel goods from Russia, as well as the export of luxury goods in the other direction.
Russia's main force had been stalled north of Kyiv, having failed in what Western analysts say was an initial plan for a lightning assault.
But images taken on Friday and released by private U.S. satellite firm Maxar showed Russian forces were continuing to deploy closer to Kyiv and firing artillery toward residential areas, according to the company's analysis.
Multiple homes and buildings were on fire and widespread damage was seen throughout the town of Moschun, northwest of Kyiv, Maxar said. Reuters could not independently verify the images.
Britain's intelligence update said Russian ground forces were still making only limited progress, hampered by logistical problems and Ukrainian resistance.
The Ukrainian general staff said Russian forces were regrouping after taking heavy losses. Ukrainian troops had pushed some back to "unfavourable positions" near the Belarus border, it said.
Kyiv's mayor, former heavyweight boxing champion Vitali Klitschko, said the capital had enough essential supplies to last a couple of weeks. Supply lines remained open.
At a meeting with Belarus President Alexander Lukashenko, Putin said there were "certain positive shifts" in talks with Kyiv, but did not elaborate.
Ukraine has raised the prospect of Moscow's ally Belarus entering the war, accusing Russia of staging "false flag" air attacks on Belarus from Ukraine to provide an excuse. The Kremlin did not respond to a request for comment.
Moscow might not have sufficient troops to achieve its goals, said Mathieu Boulegue, an expert at London's Chatham House think tank.
"You can't invade a country on a one-on-one ratio" of troops, Boulegue told Reuters. "Nobody has done it, which means that either something was wrong or they had very wrong assumptions."