The International Skating Union has apologized for what it said was a mistake in nominating a Russian figure skater's Auschwitz-themed outfit for a best costume award.

Anton Shulepov had free-skated to the theme from "Schindler's List" while wearing the costume that featured a yellow star like Jews were forced to wear during the Holocaust on a top that represented uniforms for prisoners and guards at Auschwitz, a Nazi concentration camp where more than 1 million people were killed or died.

Some in the skating world expressed offense when Shulepov sported the costume in early November at the Internationaux de France and again at the end of the month while he competed in Japan. But expressions of dismay on social media grew when the International Skating Union's unit for figure skating nominated the outfit on Dec. 1 for an end-of-year award for best costume.

Russia's Anton Shulepov performs in Sapporo, Japan, on Nov. 23, 2019. Junko Kimura-Matsumoto / AFP - Getty Images

The "nomination is extremely offensive to the Jewish people as a whole," one Twitter user wrote. "Please do not promote anti-Semitism on your platform."

"I am truly shocked at the inclusion of Anton Shulepov’s free skate costume in the best costume list. It is irresponsible and offensive. The horrors of genocide is not entertainment. Remove it immediately," another Twitter user wrote.

The ISU on Monday wrote in a statement on Twitter that it had included Shulepov's free-skate costume by mistake and had meant to nominate his short-program outfit — a solid navy blue turtleneck and black pants — for best costume instead.

"This error has been corrected and the ISU sincerely apologizes for this mistake and the bad sentiments it has caused," the organization's statement said.

Russia's Anton Shulepov performs in Sapporo, Japan, on Nov. 22, 2019. junko Kimura-Matsumoto / AFP - Getty Images

The Anti-Defamation League's leader said that considering the ISU posted a picture of the Auschwitz-themed costume when nominating it, its apology was inadequate.

"Shulepov’s evocation of painful Holocaust imagery in his routine was insensitive & offensive. It's also shocking the @ISU_Figure initially posted a picture of this costume as a nominee for 'costume of the year,' and then issued a wholly inadequate apology," said a tweet by Jonathan Greenblatt, the CEO of the ADL.