ISIS terror group could target the Rio Olympics with a dirty bomb, it is feared.
United nations security experts have sent sophisticated detection equipment to Brazil to help combat any potential threat.
The International Atomic Energy Agency (IAEA) has provided personal and portable radiation monitors for use by officials throughout the games – which start on Friday.
Brazil’s head of anti-terrorism believes there is “credible threat” Islamic State will target Rio next month and has put “numerous measures” in place, reports The Sun.
Luiz Alberto Sallaberry said the threat had increased dramatically in recent months due to attacks across Europe.
He added there was a rise in the number of Brazilian nationals thought to sympathise with the terrorists.
Earlier nuclear experts claimed a ‘dirty bomb’ terror attack on a European city is more likely than at any time since the end of the Cold War, nuclear experts claim.
Islamic State terrorists want to seize nuclear materials to strike terror in the West and have already launched many chemical attacks in Iraq and Syria.
The group attacked rebels and government forces in Iraq and Syria and militants linked to both the Paris and Brussels attacks are thought to have studied a Belgian nuclear power plant.
Moshe Kantor, head of the Luxembourg Forum on Preventing Nuclear Catastrophe, warned: “ISIS has already carried out numerous chemical weapons attacks in Syria.
“We know it wants to go further by carrying out a nuclear attack in the heart of Europe.
“This, combined with poor levels of security at a host of nuclear research centres in the former Soviet Union mean the threat of a possible ‘dirty-bomb’ attack on a Western capital is high.”
He warned the US and Russia to co-operate on using their technological resources to monitor the illegal transportation of radioactive materials.
Brussels suicide bomber brothers Khalid and Ibrahim El Bakraoui had originally planned an attack on a nuclear site in Belgium and had filmed the routine of the head of Belgium’s nuclear research and development programme.
On Tuesday the Kurdish military warned IS is planning on using chemical weapons in future suicide bombings.
Peshmerga General Akram Mohammed Abdulrahman said that while ISIS has previously used chemical weapons and suicide bombings separately, they are now looking to combine them, training brainwashed teenage insurgents to carry out suicide bombings using munitions containing harmful chemicals.
The warning comes after claims the police force guarding Britain’s nuclear arsenal is operating “at the limits of its resources”
Chairman of the Defence Police Federation Eamon Keating spoke out as the civilian Ministry of Defence Police (MDP) faces a potential further reduction of 15% in its workforce.