Moldovan police working with the FBI are reported to have stopped four attempts by smugglers to sell nuclear material to extremists in the Middle East over the past five years.

The most recent case was in February when undercover agents were offered a large amount of radioactive caesium, the Associated Press reports.

Investigators say much of the material is believed to come from Russia. They say some gangs have alleged links to Russia's intelligence services. 

Police and judicial authorities in Moldova shared information with AP to highlight how dangerous the nuclear black market has become, the news agency says.

They say the deterioration in relations between Russia and the West has made it more difficult to know whether smugglers are succeeding in selling radioactive material originating from Russia abroad.

Moldova is a former Soviet republic.

Read more: BBC News