Barack Obama has warned that the prospect of Isis or other terrorists getting hold of a nuclear bomb is among the most serious threats faced by the world.
Speaking during the international Nuclear Security Summit in Washington DC, the US President said it was clear that “these mad men” would use such a device to kill as many people as they could.
David Cameron, who also attended the meeting, offered British help to other countries to ensure terrorists could not get hold of radioactive materials.
It is feared Isis could detonate a “dirty bomb” – in which conventional explosives are used to disperse radioactive particles over a wide area – or even make a bomb capable of creating a fission explosion and producing the dreaded mushroom cloud.
Mr Obama said the risk of Isis or other extremists getting a nuclear weapon remains “one of the greatest threats to global security”, adding that Isis had already used chemical weapons and that al-Qaeda had long sought nuclear material.
Fear and frustration: The Nuclear Security Summit
The Nuclear Security Summit in Washington is the fourth and final of Barack Obama’s presidency. It is not certain whether the meetings, which he established, will continue after he leaves office next year.
For the dozens of world leaders assembled in Washington this week, the harrowing risk of nuclear terrorism has been at the forefront of their discussions, alongside concerns about North Korea’s nuclear weapons programme.
Frustration over the slow pace of reducing nuclear stockpiles has shadowed this year’s summit, Mr Obama’s last major push on denuclearisation. The absence of key players — especially Russia — further underscored the lack of unanimity still confronting global efforts to deter nuclear attacks.
“There is no doubt that if these mad men ever got their hands on a nuclear bomb or nuclear material, they would certainly use it to kill as many people as possible,” he said.
Security concerns at civilian nuclear infrastructure were raised after reports that two of the Brussels bombers may have carried out surveillance on the home of a security official at a Belgian nuclear facility.
Mr Cameron said British expertise would be offered to other countries to secure nuclear facilities.
“We know that the terrorists we face today would like to kill as many people as they possibly could, using whatever materials they can get their hands on,” Mr Cameron said.
“So obviously the security of nuclear materials, for those countries that have nuclear programmes, is incredibly important.”
A British government source said there was no “credible evidence” that terrorists were targeting British facilities.
Dr Beyza Unal, a research fellow in nuclear weapons policy at Chatham House, said there was currently no evidence that terrorists could build a nuclear weapon.
But she added that world leaders needed to act to strengthen security not just at civilian nuclear facilities but also nuclear weapons sites, and warned of an “insider threat” at nuclear facilities. Psychological assessments and cyber-security training for employees should be considered to mitigate risks, she said.
Technological advances, including the advent of 3D printing, have “added to the challenge” of preventing terrorists obtaining radioactive or chemical weapons, a Government strategy document warned last week.