Thousands Escape From Ukrainian Cities as Russia, Ukraine Trade BarbsThousands of Ukrainians fled brutal fighting in some of the country's key population centers Friday despite problems with maintaining some of the pre-identified humanitarian corridors. A senior Ukrainian official said a total of 6,266 people were able to evacuate and flee the violence, including more than 3,000 from the besieged southern city of Mariupol. The escape of so many civilians from Mariupol came despite a failed attempt to evacuate even more people from the city that U.S. defense officials said had been "decimated" by Russian airstrikes and missile attacks. An attempt to reach the city with buses and rescue personnel failed after "arrangements and conditions made it impossible to proceed," the International Committee of the Red Cross said Friday. "For the operation to succeed, it is critical that the parties respect the agreements and provide the necessary conditions and security guarantees," the ICRC said in a statement. "(The team) will try again on Saturday to facilitate the safe passage of civilians from Mariupol." Earlier Friday, Donetsk regional Governor Pavlo Kyrylenko accused Russia of breaking its promises to allow for a humanitarian corridor. "Humanitarian deliveries, despite all the agreements and promises of the Russian side, are not being carried out," he said during a televised address. Reports from the region indicate that many of those who did manage to escape left Mariupol on foot. Ukrainian President Volodymyr Zelenskyy said in a video address Friday that Ukraine is discussing separately “the evacuation of the injured and our killed military personnel and civilians.” He said the discussions are taking place with Turkey, which is acting as an intermediary with Russia. Zelenskyy’s office said Friday that 86 Ukrainian service members were freed as part of a prisoner exchange with Russia. It did not disclose how many Russian soldiers were released. Ukrainian momentum Ukrainian cities, including the capital of Kyiv, remained under heavy bombardment from Russian forces despite a Russian promise earlier in the week to de-escalate its military campaign in the north of the country. Kyiv Mayor Vitali Klitschko said Friday that huge battles were also being fought to the north and east of the capital. "The risk of dying (in Kyiv) is pretty high," he said. "My advice to anyone who wants to come back is 'Please, take a little bit more time.'" But Ukrainian and Western officials also reported signs of progress for the Ukrainian military, saying it had some Russian forces on the run, including in key areas around the capital. "Our troops are chasing them both to the northwest and northeast, pushing the enemy away from Kyiv," said Oleksiy Arestovych, a political adviser to Zelenskyy. British military intelligence backed up some of the Ukrainian claims. Ukrainian forces "continued to make successful but limited counterattacks to the east and northeast of Kyiv," Air Vice-Marshal Mick Smeath, the British defense attaché in Washington, said in a statement. "Ukrainian forces have retaken the villages of Sloboda and Lukashivka to the south of Chernihiv and located along one of the main supply routes between the city and Kyiv," Smeath added. Russian accusations Ukrainian officials denied Russian accusations that Ukrainian forces successfully carried out a cross-border helicopter strike on an oil depot in the Russian city of Belgorod, about 35 kilometers from the border. "For some reason they say that we did it, but in fact this does not correspond with reality," Oleksiy Danilov, secretary of Ukraine's national security council, said on national television. Russia's regional governor said the strike caused several fires and wounded two people. Kremlin spokesperson Dmitry Peskov further warned the strike could have a detrimental effect on peace talks, which resumed Friday via video link. "Certainly, this is not something that can be perceived as creating comfortable conditions for the continuation of the talks," he said. The White House on Friday declined to comment on the Russian allegations, noting the Ukrainian denials, and rejected Moscow's assertion that Kyiv should shoulder any blame for hindering peace talks. "There is one aggressor here — that is President (Vladimir) Putin and the Russian military at his direction," White House press secretary Jen Psaki told reporters. "This is a war that President Putin started, a brutal war with Russia's forces continuing to bombard cities across Ukraine and commit terrible acts of violence." Psaki also confirmed reports that the U.S. was providing Ukrainian forces with protective gear "that could be deployed in the event of Russia's use of a chemical and biological weapon." U.S. and NATO officials have been warning for weeks that Moscow could be considering the use of chemical or biological weapons as part of a so-called false flag operation to justify further Russian military escalation. More recently, officials have said they have not yet seen evidence of an imminent attack, though U.S. Department of Defense officials told lawmakers Friday they remained concerned about both the potential use of chemical weapons and Russia's ongoing disinformation campaign in which it accuses the U.S. of funding bioweapons labs in Ukraine. "I can say to you unequivocally there are no offensive biologic weapons in the Ukraine laboratories that the United States has been involved with," said Assistant Secretary of Defense Deborah Rosenblum. The latest concerns come as U.S. and other Western defense and intelligence officials warn that Moscow is repositioning its forces in preparation for what the Kremlin has said will be a renewed focus on the Donbas region in eastern Ukraine. Russian repositioning Ukrainian authorities estimate Russia overnight withdrew 700 units of equipment from the Kyiv region, moving them back to Belarus. General Oleksandr Gruzevych, deputy chief of staff of Ukraine's armed forces, said the number of Russian forces on the move was "pretty significant." But U.S. defense officials have said it is likely only a matter of time before the Russian units are refitted and resupplied and sent back into the war zone. Additionally, officials have warned that Russia is transferring more missile units to Belarus — a possible prelude to an intensification of ballistic missile attacks on targets across Ukraine. And they note there has been little to no letup in air and missile strikes on key cities including Kyiv and Chernihiv. International pressure Turkish President Recep Tayyip Erdogan spoke by phone with Putin on Friday, according to Erdogan's office, urging Moscow and Kyiv to "act with common sense." Erdogan's office said the Turkish leader had pushed for Putin to maintain a dialogue with Ukraine's leader. China also said Friday it would push for peace. Chinese Premier Li Keqiang told European Union leaders during a virtual summit that Beijing would encourage a peaceful settlement in "its own way." Western officials have voiced concern that Beijing might aid Russia by providing its military with weapons and other assistance, though they admit there have been no signs of such help so far. "We called on China to help end the war in Ukraine. China cannot turn a blind eye to Russia's violation of international law," European Council President Charles Michel told reporters during a news conference following the summit. Jamie Dettmer contributed to this report from Vinnytsia, Ukraine. Anna Chernikova and Margaret Besheer also contributed. Some information came from The Associated Press and Reuters.