Britain Prime Minister David Cameron warned Western leaders Friday the Islamic State plans to use drones to spray nuclear material over Western cities.

The UK Daily Telegraph reported that there is growing concerns among world leaders that extremists are looking to buy commercial drones to launch a dirty bomb attack over major metropolitan cities, which could kill thousands.

Cameron warned the dangers of ISIS getting hold of nuclear material were “only too real.” He met with leaders from the U.S. , France and China to plan out a reaction response to such an attack, the newspaper reported.

US officials reportedly fear that extremists could steal radioactive material from a medical facility and sold through the “dark web.” Cameron said he would deploy counterterrorism police and the UK Border Force while British leaders hold a Cobra meeting.

“We have already seen (ISIS) trying to look at whether they can get their hands on low-level crop-using-type drones,” one British official told The Telegraph.

The Islamic State is believed to have seized about 90 pounds of low-grade uranium from Mosul University in Iraq after capturing the city in 2014. However, it might cause more panic than actual harm. Cameron told reporters at the nuclear summit in Washington that concerns of a nuclear attack were real.

“So many summits are about dealing with things that have already gone wrong. This is a summit about something we are trying to prevent,” Cameron added.

Cameron said at the summit that Britain plans to hire 1,000 more armed police and deploy counterterrorism units in cities outside London to help counter any possible attack.

Click for more from the UK Daily Telegraph.