US President Joe Biden on Friday said American officials were trying to determine precisely how Wagner mercenary chief Yevgeny Prigozhin's plane was brought down in Russia, leaving no survivors.
Russia earlier on Friday scolded Biden for expressing his lack of surprise that Prigozhin had been killed in a plane crash and cautioned that it was not appropriate for Washington to make such remarks.
Asked by reporters what brought the Wagner leader's plane down, Biden said: "I'm not at liberty to speak to that precisely ... We're trying to nail down precisely, but I don't have anything to say."
Russian President Vladimir Putin sent his condolences to Prigozhin's family on Thursday, breaking his silence after the mercenary leader's plane crashed two months after he led a mutiny against Russia's army chiefs.