Ex-army captain Bolsonaro made the announcement on Twitter, where most of his key decisions have been transmitted since he won October's presidential election.

Dos Santos Cruz joins two generals -- defense minister Fernando Azevedo e Silva and minister of institutional security Augusto Heleno -- and air force pilot and astronaut Marcos Pontes, who is the new minister of science and technology.

Unlike his government secretary predecessors, 66-year-old Dos Santos Cruz has no prior political experience, something that has not deterred Bolsonaro in several other appointments.

He was the military attache to Brazil's embassy in Moscow in 2001-02 and headed Brazil's UN peace mission to Haiti in 2006-09 as well as another mission to the Democratic Republic of Congo in 2013-15.

Internet news site G1 describes him as a general who "likes to be on the front line," pointing to an episode in 2015 when the helicopter he was travelling in was targeted by Congolese rebels.

Current Brazil President Michel Temer appointed him head of the Secretariat of Public Security last year, but Dos Santos Cruz stepped down in June to take up a role as a UN consultant.

Bolsonaro has now named 15 members of his cabinet, which is expected to comprise around 20 people, down from the current 29 ministries.

His other appointments have been a mix of conservatives on the social plan and ultra-liberals when it comes to questions of the economy.