Brazilian President Jair Bolsonaro has officially launched his re-election campaign in Rio de Janeiro.

A recent opinion poll suggests the far-right leader is trailing as much as 19 percentage points behind his main left-wing rival, Luiz Inácio Lula da Silva.

Lula is known for his policies to lift people out of poverty.

In his nomination speech, Mr Bolsonaro promised to retain a welfare programme that makes cash payments to poorer Brazilians.

The first round of the election will be held on 2 October with a second round scheduled for 30 October if none of the candidates gets 50% of the votes.

Mr Bolsonaro's candidacy was officially endorsed by his right-wing Liberal Party.

During a rally at the Maracanãzinho stadium, Mr Bolsonaro again referred to his claims that Brazil's voting system is "flawed".

The president has repeatedly alleged - without providing any evidence - that the current electronic system is open to fraud.

The allegation has been dismissed by Brazil's electoral tribunal as "disinformation" and the Supreme Court has opened an investigation into Mr Bolsonaro for making the unfounded claims.

In his speech, Mr Bolsonaro, who is a former army captain, suggested to his supporters that the army shared his concerns.

"The army is on our side. It's an army that doesn't accept corruption, doesn't accept fraud," he said.

During the event, Mr Bolsonaro also announced that former defence minister General Walter Braga Netto would be his vice-presidential running mate.

Lula, who previously served as president from 1 January 2003 to 1 January 2011, was officially nominated by the left-wing Workers' Party on Thursday.