The International Atomic Energy Agency (IAEA) has loaned hi-tech radiation monitors - including personal detectors and portable scanners - for use on the ground throughout the Games.

EXPERTS from the United Nations have sent state-of-the art detection equipment to Brazil over fears suicidal terror nuts will target the Olympics with a devastating 'dirty bomb'.

Troops in hazmat suits rehearse a 'dirty bomb' attack outside the National Stadium

4 A 'dirty bomb' is a weapon which combines radioactive material with explosives Credit: AP:Associated Press

Brazil's anti-terror chief has already admitted there is a 'credible threat' ISIS will target Rio next month and said 'numerous measures' are being taken to prevent any attack.

Counter terrorism director Luiz Alberto Sallaberry said the threat had increased dramatically in recent months due to attacks across Europe.

He also pointed to a rise in what he described as the number of Brazilian nationals suspected of sympathising with ISIS militants.

The 'dirty bomb' fears increased following the attacks in Brussels amid claims the brothers at the heart of the plot had tried to obtain nuclear materials so they could build their own bomb.

A dirty bomb or radiological dispersal device (RDD) is a weapon that combines radioactive material with conventional explosives.

It can be easily assembled and prove extremely devastating.

The purpose of the weapon is to contaminate the area around the explosion with radioactive material.

Experts say although stealing and detonating a nuclear weapon is highly unlikely, a small amount of radioactive material could be combined with explosives to make a dirty bomb capable of contaminating a vast area.

There are also fears sufficient material could be fashioned into a crude vehicle-borne driveable atomic weapon.

Earlier this year, Ben Rhodes, Barack Obama’s deputy national security adviser, said a nightmare radioactive attack is a big fear.

4 Officers in Seattle hold a huge bio-terrorism drill to highlight the dangers Credit: AP:Associated Press

4 Armed police stand guard outside the Olympic Athletes Village Credit: Getty Images

He said: “We have seen ample proof that terrorist organisations like Isil have no regard for innocent human life or international norms, and that only redoubles the need for us to have effective international nuclear security approaches.”

The IAEA is widely known as the world's "Atoms for Peace" organisation within the United Nations family.

Set up in 1957 as the world's centre for cooperation in the nuclear field, the Agency works with its Member States and multiple partners worldwide to promote the safe, secure and peaceful use of nuclear technologies.

The Vienna-based body said: “Upon request and under the terms of the Convention on Assistance in the Case of a Nuclear Accident or Radiological Emergency, (we are) also prepared to provide assistance in the event of a nuclear or radiological emergency.”