(CNN) -- A Jewish human rights organization on Monday called for Thailand's Christian leaders to condemn a parade at the Sacred Heart School in Chiang Mai, Thailand, in which participating students wearing Nazi uniforms performed "Sieg Heil" salutes.
The Simon Wiesenthal Center, a Jewish human rights organization based in Los Angeles, denounced the event, saying it was "glorifying Nazis."
Photographs of the parade show participants carrying a Swastika flag, performing Nazi salutes and wearing SS uniforms, while others dressed as Adolf Hitler complete with toothbrush moustache.
Rabbi Abraham Cooper, associate dean of the Simon Wiesenthal Center, said the images made it clear that the event could not have taken place without the knowledge and cooperation of the school administration.
"It is difficult to calculate the hurt such a display inflicted on survivors of the Nazi Holocaust and the families of all victims of Nazism. There can be no justification for such an outrage to emanate from place of learning," he said.
The Simon Wiesenthal Center urged those responsible for the school to take immediate action against the individuals who promoted and facilitated the event.
Cooper said that a similar parade took place in 2007 at a school in Bangkok in which 200 students participated, and that more recently, members of Thai rock band Slur donned Nazi uniforms in a music video. On Wednesday, the school's website posted a letter by its director expressing an apology. "We, the entire Sacred Heart School [personnel] are deeply saddened by this incident." The letter explained that the sports day activity involved groups being differentiated by colors -- the "Red" group having used Nazi symbols.
CNN's Kocha Olarn contributed to this report.