An undercover expose of neo-Nazis has sparked widespread disgust and shock this week in Poland, a country where Adolf Hitler's regime murdered millions of people in concentration camps, ghettos and in the bombing of cities.

Leaders have condemned the extremists and launched an investigation that has already led to the detention of six people and the confiscation of fascist paraphernalia and ammunition. There is widespread disbelief that young Poles, whose own ancestors were among the victims of World War II, could embrace such an ideology.

President Andrzej Duda said the neo-Nazi behavior "must be eradicated with all of our might."

The debate was sparked by a report broadcast Saturday by private news station TVN24 that showed members of a Polish neo-Nazi group celebrating Adolf Hitler's 128th birthday last year.