U.S. declares a potential 'war crime'. As the death toll of Ukrainian civilians killed in Russia’s invasion of that country mounts, Russia has been accused of tactics that could be a war crime.Ukrainian officials and media say Russia has used what’s known as a thermobaric weapon, or a vacuum bomb, in its efforts to crush Ukrainian opposition.“They used the vacuum bomb today,” Oksana Markarova, Ukraine’s ambassador to the United States, told reporters on Monday, according to Politico.