The Auschwitz-Birkenau Memorial and Museum in Poland recently responded to a high-profile Japanese plastic surgeon's Twitter post denying the Holocaust by issuing a tweet in Japanese describing it as a "historic fact."
Katsuya Takasu, a well-known media personality in Japan, posted the tweet on Oct. 18, 2015.
"I think Nanjing and Auschwitz are fabricated," he wrote, apparently referring to the Holocaust along with the 1937 Nanjing Massacre, in which China claims the Japanese army slaughtered more than 300,000 people. Japanese historians have put the death toll from tens of thousands to 200,000.
The official Twitter account of the museum replied to Takasu's tweet on Friday, saying in Japanese, "Auschwitz is a historic fact that continues to warn the hearts of people around the world."
"The remains of the concentration and extermination camp created by Nazi Germany represent the greatest tragedy in human history," the post said.
The museum's Twitter account regularly tweets in multiple languages but rarely in Japanese.
Takasu reacted with a fresh post on Sunday, saying he "mistrusts a post on an old topic being brought up."
The Auschwitz concentration camp was established in 1940 in the suburbs of Oswiecim, a Polish city annexed by Nazi Germany, and over 1.1 million people, mostly Jews, were systematically killed at the camp before it was liberated by Soviet troops in January 1945.
It was designated as a UNESCO World Heritage site.