Buenos Aires - Police have seized nearly 400 kilos of cocaine from the Russian embassy in Buenos Aires and arrested several members of a drug trafficking gang, Argentina's security minister announced on Thursday.

Patricia Bullrich told a press conference that the drugs discovered in an annex of the embassy had a street value of around $50m.

"A gang of narco-criminals was trying to use the diplomatic courier service of the Russian embassy" to ship the drugs to Europe, she said.

She told reporters that Russian and Argentine police had decided to mount a sting operation after the Russian ambassador informed them of the drugs find in December 2016.

"The cocaine was replace by flour and monitoring devices were placed to monitor delivery" of the 16 bags of the drug, Bullrich said. She said the sting had resulted in the arrest of five suspects - two in Argentina and three in Russia.

The drug, of "very high purity," was destined for Russia and probably also Germany, where the suspected mastermind lives. "We believe the German police will arrest this fugitive," Bullrich said.

The minister said Russian security service agents "came to Argentina on three occasions to assist in the investigation" that took more than a year.

One of the two people arrested in Argentina is a naturalized Russian who was a member of the police force in Buenos Aires, said Bullrich.

Investigators believe the cocaine likely originated in Colombia or Peru.