A group of 11 people took off their clothes, killed a sheep and chained themselves together by the main gate of the former Nazi German death camp of Auschwitz before being detained by police, officials said Friday.

A spokesman for the Auschwitz memorial, Bartosz Bartyzel, told Associated Press their motives were not clear as they briefly stood and then sat down by the notorious "Arbeit Macht Frei" ("Work sets you free") gate in the southern city of Oswiecim on Friday afternoon.

Auschwitz inmates passed through the gate when brought into the death camp and when led by armed Nazi guards to slave labour sites.