A hugely popular right-wing Croatian singer and hundreds of thousands of his fans performed a pro-Nazi World War II salute at a massive concert in Zagreb, drawing criticism.

One of Marko Perkovic’s most popular songs, played in the late Saturday concert, starts with the dreaded “For the homeland — Ready!” salute, used by Croatia’s Nazi-era puppet Ustasha regime that ran concentration camps at the time.

Perkovic, whose stage name is Thompson after a U.S.-made machine gun, had previously said both the song and the salute focus on the 1991-95 ethnic war in Croatia, in which he fought using the American firearm, after the country declared independence from the former Yugoslavia. He says his controversial song is “a witness of an era.”