Some 130 people have been rescued so far from a bombed theatre in the city of Mariupol, Ukraine’s human rights ombudswoman said on Friday,
There is still no information on more than 1,000 other people officials believe were sheltering there when the bomb fell.
Ombudswoman Lyudmyla Denisova said rescue work was ongoing at the site, which Ukraine says was hit by a Russian air strike on Wednesday. Russia has denied bombing the theatre or targeting civilians.
“Rescuers are working. There is only this information: 130 people are alive and have been taken out. The rest are waiting for help,” she said.
There has been no confirmation of the number of possible casualties.
“According to our data there are still more than 1,300 people there who are in these basements, in that bomb shelter,” said Ms Denisova, referring to underground shelters below the theatre.
Mariupol city council has previously said there were more than 1,000 people sheltering under the theatre.
Biden and Xi video call
Meanwhile, US president Joe Biden and Chinese president Xi Jinping spoke on a video call on Friday about Russia's invasion of Ukraine and Chinese media said Mr Xi underlined that such conflicts are in no one's interests.
Biden was expected to tell the Chinese leader that Beijing would pay a steep price if it supports the invasion, a warning that comes at a time of deepening acrimony between the two nations.
The call lasted just under two hours, said the White House.
Earlier, US deputy secretary of state Wendy Sherman told MSNBC that Mr Xi should tell Russian president Vladimir Putin "to end this war of choice, this war of carnage" in Ukraine.
“China needs to stand on the right side of history. It needs to ensure that it does not backfill, financially or in any other way, sanctions that have been imposed on Russia,” she subsequently told CNN.
Mr Xi told Mr Biden that conflicts and confrontations such as the events in Ukraine are in the interests of no one, according to Chinese state media.
State-to-state relations cannot advance to the stage of confrontation, and conflicts and confrontations are not in the interests of anyone, he said.
"The Ukraine crisis is something that we don't want to see," Mr Xi was quoted as saying. Chinese state media said the call had been requested by the US side.
US secretary of state Antony Blinken said Mr Biden would make clear to Mr Xi that China will bear responsibility if it supported Russia's "aggression" and that Washington "will not hesitate to impose costs".
Russia says it is carrying out a special military operation in Ukraine.
The United States and China are the world's two largest economies and Washington has been anxious to avoid a new "cold war" between them, seeking instead to define the relationship as one of competitive co-existence.
However, China’s “no-limits” strategic partnership with Russia announced last month and its stance on Ukraine has called that into question. China has refused to condemn Russia’s action in Ukraine or call it an invasion, and it has censored online content in China that is pro-West or unfavourable to Russia.
Beijing, while saying it recognises Ukraine’s sovereignty, has also said Russia has legitimate security concerns that should be addressed. It has urged a diplomatic solution to the conflict.
Russian minister for finance Anton Siluanov said this week the country was counting on China to help it withstand the blow to its economy from punishing western sanctions
Meanwhile, President Putin appeared at a huge, flag-waving rally at a Moscow stadium and praised his country’s troops in biblical terms on Friday.
“Shoulder to shoulder, they help and support each other,” he said of Moscow’s forces in a rare public appearance since the invasion three weeks ago.
“We have not had unity like this for a long time,” he added to cheers from the crowd. Moscow police said more than 200,000 people were in and around the Luzhniki stadium for the celebration marking the eighth anniversary of Russia’s annexation of the Crimean peninsula, seized from Ukraine.
President Putin is due to have another phone call with French president Emmanuel Macron on Friday. The call follows the fresh appeal issued by world leaders for an investigation of the Kremlin’s attacks on civilian targets.
Food supplies in Ukraine
Food supply chains in Ukraine are collapsing, with a portion of infrastructure destroyed and many grocery stores and warehouses empty, a World Food Programme (WFP) official said.
“The country’s food supply chain is falling apart. Movements of goods have slowed down due to insecurity and the reluctance of drivers,” said WFP emergency co-ordinator for the Ukraine crisis Jakob Kern.
He also expressed concern about the situation in “encircled cities”. WFP buys nearly half of its wheat supplies from Ukraine and Mr Kern said that the crisis there since the Russian invasion had pushed up food prices sharply.
Ukrainian president Volodymyr Zelenskiy said he spoke with the head of the European Commission Ursula von der Leyen on Friday and Ukraine expects progress to be made on its application to join the European Union in the coming months.
Mr Blinken said on Thursday that US officials were evaluating potential war crimes and that if the intentional targeting of civilians by Russia is confirmed, there will be “massive consequences”.
Areas in cities, hospitals, schools and buildings where people sought safety from the bombardment have been attacked. In Merefa, near the northeast city of Kharkiv, at least 21 people were killed when Russian artillery destroyed a school and a community centre, a local official said.
The World Health Organisation said it has verified 43 attacks on hospitals and health facilities, with 12 people killed and 34 injured.
In a joint statement, the foreign ministers of the Group of Seven leading economies accused President Putin of conducting an "unprovoked and shameful war". The group urged Russia to comply with the International Court of Justice's order to stop its attack and withdraw its forces.
Pope Francis called the war “perverse abuse of power” waged for partisan interests which has condemned defenceless people to violence. The pope has not actually named Russia in his condemnations but he has used phrases such as “unacceptable armed aggression” to get his point across.
Earlier, the Polish border guard said more than two million refugees have entered Poland from Ukraine since the start of the Russian invasion on February 24th.
Ukraine and Russia this week reported some progress in negotiations. Kremlin spokesman Dmitry Peskov said on Thursday that some negotiators were breaking into working groups. However, western officials said a big gap remains between the two sides, adding President Putin did not seem in the mood to compromise. – Additional reporting from AP/Reuters