(Photo: CGTN)

Brazilian federal police will investigate massive amounts of disinformation circulating on social media against the two candidates vying to become president, Public Security Minister Raul Jungmann said Saturday.

The probe was announced after the Folha de Sao Paulo newspaper reported that companies had been hired to bulk transmit to many of Brazil's 120 million WhatsApp users messages attacking the leftist candidate in the race, Fernando Haddad.

Haddad accuses his far-right rival, Jair Bolsonaro, of being behind the WhatsApp campaign. He called it "defamatory" and said the contracts were illegal campaign financing requiring action from electoral authorities.

Jungmann said he was responding to a recommendation from the federal prosecutors' office that police investigate organized fake news online against both the candidates to see whether a crime had been committed.

WhatsApp has already said it was taking measures to stop companies using its service to send out bulk messages.

The app is owned by Facebook, which is under scrutiny after revelations of organized abuse of social media in 2016 to sway public opinion in the US presidential election and the Brexit referendum in Britain.