Targets include banks (about a third of bombs), police stations, army barracks, churches, embassies, the headquarters of political parties, company offices, courthouses and government buildings.
Some groups name themselves after past anarchists worldwide, including Leon Czolgosz, who assassinated US President William McKinley in 1901, and Jean-Marc Rouillan, a jailed French left-wing militant.
Hans Niemeyer, a Chilean sociologist and anarchist, was sentenced to five years' imprisonment for planting a bomb in a bank in November 2011.
Two Chilean anarchists who had been tried and acquitted in Chile were later arrested in Spain, and charged with planting a bomb in a church in Zaragoza in 2013, an attack claimed by a group named after Mateu Morral, a Spanish anarchist who attempted to assassinate the King of Spain in 1906.
An opinion poll in 2014 found that about two-thirds of Chileans feared the attacks and felt that the problem was escalating, with nearly 30 bombs in 2014 by August.