Ukrainian, Russian Troops Battle for Control of KyivWASHINGTON — Explosions and gunfire could be heard Saturday in Ukraine’s capital, Kyiv, as Russian and Ukrainian forces battled for control of the city. City officials have imposed a curfew from 5 p.m. to 8 a.m. Ukrainian officials are urging the country’s citizens to help defend Kyiv against the Russian forces. An army base in the capital was attacked but Ukraine’s military said that attack was repelled. A high-rise apartment building in the capital was hit early Saturday. Ukraine’s foreign minister said the building was struck by a Russian missile. A rescue worker told The Associated Press that six people were injured in the missile strike. Video images of the building showed extensive damage on upper floors. Ukrainian President Volodymyr Zelenskyy had predicted the attacks on Kyiv would become more intense Saturday. “Kyiv requires special attention,” he said. “We cannot lose the capital.” Zelenskyy said Saturday on Twitter that he had spoken with French President Emmanuel Macron. “Weapons and equipment from our partners are on the way to Ukraine. The anti-war coalition is working,” he tweeted. Russian forces advancing on Kyiv and other key cities as part of a plan to "decapitate" Ukraine's government appear to have lost some momentum, U.S. and Western officials said Friday, as they and Moscow ramped up information operations to keep up with fighting on the ground. A senior U.S. defense official, briefing reporters on the condition of anonymity in order to discuss intelligence, said the Russian forces had unleashed a barrage of more than 200 ballistic and cruise missiles since the invasion began, most of them targeting the Ukrainian military. "They're meeting more resistance than they expected," the U.S. official said, adding that Russian forces had yet to establish air superiority despite a numerical advantage and efforts to eliminate Ukrainian air defenses. Ukraine's command and control "is intact," the official added. In Kyiv, Zelenskyy sought to rally the nation, rejecting rumors that he had fled the city and insisting he and other government officials "are all here, defending our independence, our state." Amnesty International says Russia may have committed war crimes with its invasion of Ukraine. “The Russian military has shown a blatant disregard for civilian lives by using ballistic missiles and other explosive weapons with wide area effects in densely populated areas,” Agnès Callamard, Amnesty International’s Secretary General, said in a statement. “Some of these attacks may be war crimes. The Russian government, which falsely claims to use only precision-guided weapons, should take responsibility for these acts.” Russian claims Russian officials countered Friday that their forces had made solid progress in what they described as an effort to eliminate a terrorist threat. In one social media post, Russian Major General Igor Konashenkov said his country's forces had disabled more than 200 Ukrainian military facilities and dozens of air defense batteries and radar stations, while destroying a handful of Ukrainian combat planes, helicopters and military vehicles. Russia's military also said Friday it took control of the strategic Hostomel airport northwest of Kyiv. Russia's claim was not immediately confirmed, but Ukrainian authorities reported heavy fighting there. On the ground in Ukraine Kyiv's mayor, former world heavyweight boxing champion Vitali Klitschko, said the city has gone into a defensive phase and warned that Russian saboteurs were on the loose. Western officials, despite praising Ukrainian forces, cautioned the situation was fluid, and noted that things could change rapidly, especially given that about two-thirds of the 190,000 Russian troops along the Ukrainian border had yet to take part in the fighting. They also warned of Russian attempts to use disinformation to cloud the situation on the ground and scare Ukraine's forces into submission. "Our information indicates Russia is creating a disinformation campaign by publicizing false reports about the widespread surrender of Ukrainian troops," a U.S. official said Friday. "Our information also indicates that Russia plans to threaten killing the family members of Ukrainian soldiers if they do not surrender," the official added. Pentagon press secretary John Kirby said the United States was continuing to find ways to help Ukraine defend itself "both from a lethal and nonlethal perspective." On Friday, U.S. President Joe Biden authorized the State Department to release $350 million in military aid to Ukraine. NATO response The Pentagon voiced support for NATO's decision to activate the NATO Response Force Friday, citing Russia's aggression. "It's not entirely clear if Mr. Putin has designs beyond Ukraine, and it's because that's not perfectly clear that we continue to look for ways to bolster our NATO capabilities and to reassure our allies," Kirby said. NATO on Friday vowed to continue to support Ukraine's government and military and warned it had taken unprecedented action to ensure the security of alliance members. "We are deploying elements of the NATO Response Force on land, at sea, and in the air to further strengthen our posture and to respond quickly to any contingency," Secretary-General Jens Stoltenberg told reporters in Brussels following a virtual meeting of alliance heads of state. "There must be no space for miscalculation or misunderstanding," he said of NATO activating the 40,000-strong force for the first time. "We will do what it takes to protect and defend every ally and every inch of NATO territory." Polish officials say at least 100,000 people have crossed the Polish border from Ukraine. According to the U.N. High Commissioner for Refugees Filippo Grandi, more than 150,000 Ukrainians have now crossed into neighboring countries. White House correspondent Anita Powell, U.N. correspondent Margaret Besheer, National Security Correspondent Jeff Seldin, VOA refugee correspondent Heather Murdock in Kyiv and Jamie Dettmer in Lviv contributed to this report. VOA's Katherine Gypson contributed from Washington. Some information in this report came from Reuters.