An international organized criminal group that was engaged in illegal operations with rare metals has been uncovered in an operation carried out by Russian and Ukrainian police officers.

"We managed to uncover an international criminal group. Four of its members have already been detained, all of them will go on trial," Kursk region police chief Viktor Bulushev told journalists on Tuesday.

"A total of $240,000 worth of osmium-187, a rare-earth valuable metal, were confiscated during the joint operation," Bulushev said.