Security remains an area of concern in the build-up to next week's Games ©Getty Images

Prosecutor Rafael Brum Miron has claimed the potential terrorist plot at next month’s Olympic Games in Rio de Janeiro was “no joke” following the arrest of 12 suspects earlier this week.

Miron was responding after Brazil’s Justice Minister Alexandre Moraes sparked controversy when describing those detained as “amateurs”, with concerns raised that his comments sent the wrong message at a time when the whole world is on red alert.

The prosecutor insisted that the threat had been genuine, despite American intelligence suggesting there was "no clear evidence" that those in the group were linked to Islamic State.

"They were amateurs, but they were not a joke," Miron told Reuters.

"There's no such thing as an experienced suicide bomber.

"Our police and intelligence agencies are continuing to monitor more than 100 people so that we can have tranquility during the Games.”

Ten people were arrested on Thursday (July 21) by federal officers following a covert operation carried out by the police's anti-terrorism division, to thwart what was seen as the biggest threat to the security of the Games so far.

An eleventh suspect handed himself into police on Saturday (July 23), while another member of the group was detained the following day.

Police made their move after monitoring messages shared by the group on social networks Facebook and Twitter, as well as instant messaging application WhatsApp.

Around 85,000 soldiers, police officers and security personnel are due to be working during the Games ©Getty Images
Around 85,000 soldiers, police officers and security personnel are due to be working during the Games ©Getty Images

As well as discovering details of a planned attack, investigators also uncovered evidence of weapons which had been purchased.

Federal Police in the South American nation claim that some members of the group were on their watch list after they accessed Islamist websites.

Miron has claimed that police are now investigating possible connections with Islamist groups in Africa, with two members of the group allegedly coming from the continent.

It was revealed that the French team was the target of a terrorist plot by a Brazilian Islamist earlier this month.

Around 85,000 soldiers, police officers and other security personnel are expected to be deployed at the Games, representing a significant increase on the amount which policed London 2012.

However, hundreds of Brazilian National Force officers have threatened to quit over poor accommodation and working conditions.

Rio Mayor Eduardo Paes has been publicly critical of the State Government in the city over their security plans, lambasting them for doing a "terrible, horrible job".