A Jewish NGO denounced K-pop group BTS on Sunday for "denigrating the memory of the past" after its members wore hats with the Nazi logo and one member wore a T-shirt celebrating the U.S. atomic bombing of Japan.

"It goes without saying that this group...owes the people of Japan and the victims of Nazism an apology," said Rabbi Abraham Cooper, director of Global Social Action of the Simon Wiesenthal Center, in a statement.

(Fans await a BTS concert in Los Angeles) [Getty/Kyodo]

The center said that members of the band had posed for a photo shoot wearing hats with the Nazi SS Death Head logo. It also described the flags appearing on their concert stage as "eerily similar to the Nazi Swastika."

A Japanese TV broadcaster recently canceled a concert by the group amid controversy over one of its members having worn a T-shirt with printed photos of an atomic bomb exploding and people in celebration.

The center also criticized the band for "mocking the victims" of the bombing.

Their actions would make the younger generation around the world more likely to "identify bigotry and intolerance as being 'cool' and help erase the lessons of history," said Cooper.

BTS, also known as the Bangtan Boys, is a seven-member South Korean boy band that debuted in 2013. In May this year, it reached the top of the Billboard 200 album chart with its release "Love Yourself: Tear."