Russia’s president has mocked United States President Joe Biden for labelling him a killer – saying “it takes one to know one.” The war of words comes after President Biden was asked in an interview whether he believed Vladimir Putin was a killer, to which he responded “I do.” Putin was accused of ordering the poisoning of Russian Opposition Leader Alexei Navalny, a claim the president strongly denied. The White House responded to the exchange - confirming Mr Biden was standing firm on his remarks.