Georgian authorities have imprisoned a Russian citizen for attempting to sell 100 grams (3.5 ounces) of weapons-grade uranium after a joint operation with the

FBI, officials announced.

Georgia’s security services arrested Oleg Khiltsagov as he tried to sell “100 grams of 90-percent enriched uranium” in the sting operation last year, said the interior ministry’s analytical department chief, Shota Utiashvili.

The material appeared “to be ready for an atomic bomb,” the ministry said in a statement, although experts say a total of between 15 and 25 kilograms of highly-enriched uranium is needed to make an atomic bomb.

The UN nuclear agency warned that the operation, which took place over the first half of last year, could point to a greater availability of nuclear material on the black market.

Utiashvili said that a Georgian officer posed as a buyer from a radical Islamic group and encouraged Khiltsagov, who was trying to sell the uranium in Russia, to travel to Georgia.

Khiltsagov tried to sell the uranium for one million dollars (770,000 euros) and was caught with the radioactive substance in a plastic bag in his pocket, he said.

Khiltsagov, who comes from the province of North Ossetia in southern Russia, was sentenced to eight years prison in June and three Georgian nationals were also arrested in the operation, he added.

US law-enforcement authorities confirmed they had taken part in the sting.

“The FBI was a participant in this joint investigation and worked well with our partners. This was a successful case. We have no further comment,” the Federal Bureau of Investigation said in a statement.

The Georgian interior ministry official said details of the operation had only been revealed now, several months after the event, because “we were concerned that there were other accomplices.”

Georgian authorities have been in contact with Russia over the case and Georgian interior ministry officials have handed some of the uranium seized to their Russian counterparts for analysis, Utiashvili said.

But an official from the Russian nuclear agency Rosatom was quoted by Interfax news agency as saying that the quantity of uranium was “minimal” and “did not allow us to establish the country of origin.”

Rosatom’s press service in Moscow could not be reached for comment.

Melissa Fleming, a spokeswoman for the UN’s

International Atomic Energy Agency (IAEA), said the Georgia case was of “very high concern” and could point to larger trafficking problems.

An IAEA data bank lists 16 cases of incidents involving smuggling or reported loss of highly enriched uranium or plutonium between 1993 and 2005, many of them in the former Soviet Union.

An official at the Russian embassy in Tbilisi confirmed that a Russian citizen had been arrested but expressed surprise at the “publication of an old story,” Interfax reported.

Georgia’s foreign ministry said the case highlighted the problem of smuggling through the separatist provinces of Abkhazia and South Ossetia that “increases the threat of proliferation of weapons of mass destruction.”

The two pro-Moscow provinces broke away from Georgia in the 1990s.