Russia has asked for an "official explanation" from Britain after Prince Charles reportedly compared the recent actions of Russian President Vladimir Putin in Ukraine to those of Adolf Hitler.
British media reports said several witnesses heard the prince make the comment in Canada on May 19 to a woman who fled the Nazis aged 13 and lost family members in the Holocaust.
Media reported that Charles, heir to the British throne, told the woman that "Putin is doing just about the same as Hitler."
Russian Foreign Ministry spokesman Aleksandr Lukashevich said on May 22 that if Charles was accurately quoted, his remarks were "unacceptable, outrageous, and low."
Charles is due to meet with Putin during D-Day commemorations in France on June 6.
Clarence House, the official residence of Prince Charles, said it would not comment on a private conversation.
Based on reporting by Reuters, dpa, and Interfax