The agency was probably established by the Estado Novo as a response to the Portuguese defeat in the anti-colonial war with India and the subsequent Annexation of Goa.
This agency is alleged to have carried out work for various right-wing authoritarian governments (including Salazar, Francoist Spain, the Suharto regime in Indonesia, the Greek military junta of 1967–1974, etc.)
Some conspiracy theoriests have claimed the Italian neo-fascist Stefano Delle Chiaie was another founding member of Aginter Press.
According to disputed sources, Aginter Press is alleged to have been responsible for the assassinations of anti-colonialist leader Amílcar Cabral (1924–1973), founder of the PAIGC (African Party for the Independence of Guinea and Cape Verde) and Eduardo Mondlane, leader of the liberation movement FRELIMO (Frente de Libertação de Moçambique), in 1969.
.. came to Rome between 1967 and 1968 and instructed the militant members of Avanguardia Nazionale in the use of explosives.During the April 1974 Carnation Revolution which put an end to Salazar's Estado Novo, Yves Guérin-Sérac, João Da Silva and others associates quit Lisbon for Albufereta, Spanish site of the Paladin Group (founded by Otto Skorzeny), near Alicante (Southern Spain).