Valdir Pereira da Rocha was released on a licence following his initial arrest in July, with the condition he wore an ankle tag, Globo reports.

He was sent back to prison after allegedly committing another offence last month, but is now reportedly on life support after being attacked.

According to Globo, Da Rocha’s family now have the decision on whether to continue to keep his body functioning via the life support machine.

Last month, prosecutors were found to have had gathered "sufficient evidence to proceed to trial" against eight men who had been arrested due to an alleged terror plot. 

It came after federal officers swooped to apprehend a group of ten in July, who had reported links to Islamic State (IS).

A covert operation was carried out by the police's anti-terrorism division to thwart what was then seen as the biggest threat to the security of the Olympic Games, just 15 days before the Opening Ceremony was held on August 5.

Police made their move after monitoring messages shared by the group on social networks.

Brazilian Minister of Justice Alexandre de Moraes had initially 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 was on red alert.

Prosecutor Rafael Brum Miron then claimed the potential terrorist plot was "no joke".

Around 85,000 soldiers, police officers and other security personnel were deployed at the Olympic Games, which ran until August 21.

This represented a significant increase on the amount which policed London 2012.