By Stefan J. Bos
Europol, which coordinated and supported the operation, says a crime group attempted to sell "radiological material to an army" for some 3 million euros.
The police organization said the material was purported to be uranium-235, an isotope that can be used as a fuel for nuclear power plants, or also in atomic weapons.
Officials said a Moldovan undercover agent infiltrated the ring.
These ring involved suspects in Austria and Moldova, one of Europe's most impoverished nations and a former Soviet republic.
Europol revealed that three people were detained in Vienna on November 24, one of whom has a previous conviction related to such activities.
Video footage and photos produced by Interpol show members of Austria's special police forces detaining people.
They were earlier surrounding a black car in a parking lot, pointing guns at the driver's side, and smashing in a back window with a baton.
The video, which was seen by Vatican News, also focuses on two men, their faces blurred out. They seem to walk out of the Chisinau airport in Moldova, with one carrying a bag. It then shows three men outside talking, then back inside a building.
A closeup which was taken outdoors then shows a hand grabbing a light green cylinder out of a bag and turning it to display it for the camera. It happens before cutting to a different shot of a bag full of stacks of 500-, 200- and 100-euro bills.
There is no commentary explaining the images on the video.
However, Moldovan police confirmed their involvement and said the three suspects had been monitored for the past year. They did not provide further information.
Austrian authorities refused to comment on the case.
News about the smuggling of nuclear material comes after Pope Francis expressed his concerns about nuclear weapons.
He called both the use and the possession of nuclear weapons "immoral," and he said it must be added to the Catechism of the Catholic Church.