"An organized criminal group's activities were thwarted and heroin weighing a total of about 50 kilograms seized," the agency said.
The operation was conducted in the Shelkovsky district 25 kilometers (15 miles) northeast of Moscow in the early hours of Sunday, when a gang member came to retrieve heroin from a stash concealed in a dump.
He was caught with 4 kilograms (8 pounds) of heroin on him, the agency said. The other 42 kilograms (90 pounds) were discovered in the stash. The seven other gang members were arrested later Sunday.
The agency said the batch was enough to make 1.5 million doses, which would have brought in over $600,000 to wholesalers and a total of over $78 million to street-level dealers.
Investigators have yet to determine the roles those detained played in the gang, the smuggling routes taken and the means used to deliver the heroin, the agency said.