London: The Sunni jihadi organisation, Islamic State (IS) may have armed itself with a "dirty bomb", having stolen 40 kg of uranium from an Iraqi university, media reported.

Militants boasted of the device on social media, with one even commenting on the destruction such a bomb would wreak in London, four months after the chemical went missing from Mosul University, the Daily Mail reported Sunday.

One of the extremists making online threats to the West is British explosives expert Hamayun Tariq, who fled his home in Britain for the Middle East in 2012.

Using the alias, Muslim-al-Britani, he tweeted, “O by the way, Islamic State does have a dirty bomb. We found some radioactive material from Mosul University,” according to a report in The Mirror, which the Daily Mail cited.

He wrote: "We'll find out what dirty bombs are and what they do. We'll also discuss what might happen if one actually went off in a public area.”

He noted that such a bomb would be more of a disruptive than a destructive weapon.

After pledging his allegiance to the Taliban, Tariq claimed to have been recruited by IS fighters, who paid for him to travel to Syria to join them.

Other jihadis also echoed the claims that a destructive dirty bomb has been made.

These claims by the extremists are certain to raise the concerns of the forces fighting the IS and other terrorist groups in Iraq, Syria and other parts of the world.

Iraq's Ambassador to the UN Mohamed Ali Alhakim told UN Secretary-General Ban Ki-moon that “terrorist groups have seized control of nuclear material at the sites that (went) out of the control of the state”, adding that such materials “can be used in manufacturing weapons of mass destruction”.

“These nuclear materials, despite the limited amounts mentioned, can enable terrorist groups, with the availability of the required expertise, to use them separately, or in combination with other materials in terrorist activities,” Alhakim said.

If the jihadis' claims of possessing a dirty bomb were true, the US and its allies would face a tough task to win the war against global terror.