An escalation of violence by neo-Nazi skinheads has authorities concerned that they must be brought under control or become a danger to society. Skinheads engaged in a vicious attack on an anti-fascist concert in Valparaiso, and others are active in Puente Alto, Santiago’s most densely-populated neighborhood, and in the southern cities of Osorno and Valdivia. They often attack leftist youths and immigrants, so avoiding political rallies sponsored by either group is prudent.