Brazil's anti-terror chief has admitted there is a 'credible threat' that ISIS will target the Rio Olympics and that numerous measures are being taken to prevent an attack.

With just three months until Games begin, the Brazilian national intelligence agency said the country is preparing for all eventualities.

Brazil has long regarded itself as an unlikely target of extremists thanks to its historical standing as a non-aligned, multicultural nation that is free from enemies.

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Brazil's anti-terror chief has admitted there is a 'credible threat' that ISIS will target the Rio Olympics. Pictured is the Maracana Stadium where the opening ceremony will take place

However, counter terrorism director Luiz Alberto Sallaberry said in a statement the threat had increased in recent months due to attacks in other countries, and a rise in what he described as the number of Brazilian nationals suspected of sympathising with Islamic State militants.

Mr Sallaberry also confirmed that a credible threat to state security had been made last year.

A tweet threatening Brazil sent in November by Maxime Hauchard, a French national identified as an executioner in Islamic State propaganda videos, was genuine.

The tweet read: 'Brazil, you are our next target.'

A tweet threatening Brazil sent in November by Maxime Hauchard, piictured, a French national identified as an executioner in Islamic State propaganda videos read: 'Brazil, you are our next target'

Mr Sallaberry said his agency had taken several measures to avert a potential attack, including sharing information with foreign security forces and improved training.

But security experts have warned that many Brazilian officials do not realize how big a stage the Olympics is for anyone seeking to sow terror, either through an attack on game venues, infrastructure nearby or the athletes and 500,000 tourists expected to attend.

Brazilian officials, eager to pull off South America's first Olympics after successfully hosting the soccer World Cup in 2014, have said previously they will ensure a safe games starting August 5.

Olympic organisers plan to deploy around 85,000 security personnel for the games, double the number used in London in 2012.

A Brazilian army soldier flies over the X-Park at the Deodoro Sport Complex, which will host cycling and equestrian events, as part of a security training exercise

Soldiers jump out of a Brazilian military helicopter during a training exercise. Olympic organisers plan to deploy around 85,000 security personnel for the games

A large part of this group will be members of the National Force for Public Security, a body of police and other law enforcement officials whose commander stepped down last month amid reports he had criticized embattled President Dilma Rousseff.

Meanwhile earlier this week, it was announced that the brother of one the Brussels suicide bombers is set to compete for Belgium's taekwondo team at the Olympic Games.

Mourad Laachraoui, 21, won gold at the European Taekwondo Championships, meaning he will be travelling to South America this summer.

Mourad Laachraoui, left, brother of Brussels bomber Najim Laachraoui, right, is set to represent Belgium in Taekwondo at the games

His 24-year-old brother Najim was one of two suicide bombers who blew himself up at Brussels Airport on March 22, killing 32 people.

After the Brussels attacks, Laachraoui distanced himself from his brother, saying he'd had no contact with Najim since he left for Syria in 2013.