Nazi Germany used six extermination camps (German: Vernichtungslager), also called death camps (Todeslager), or killing centers (Tötungszentren), in Central Europe during World War II to systematically murder over 2.7 million people – mostly Jews – in the Holocaust. The victims of death camps were primarily murdered by gassing, either in permanent installations constructed for this specific purpose, or by means of gas vans. The six extermination camps were Chełmno, Belzec, Sobibor, Treblinka, Majdanek and Auschwitz-Birkenau. Auschwitz and Majdanek death camps also used extermination through labour in order to kill their prisoners.