Police in Argentina have foiled a plot to smuggle cocaine to Europe through the Russian embassy’s diplomatic courier service, following an elaborate sting operation involving a shadowy Moscow intelligence chief.

Five suspected members of the ​drug gang, including a former accountant at the embassy and a Buenos Aires police officer, have been arrested in Argentina and Russia.

But the alleged head of the network, a mysterious Russian businessman known only as “Señor K”, remains at large.

The plot was discovered by the Russian ambassador in December 2016 when he came across nearly 400kg of the drug inside 12 suitcases in an storage facility belonging to the diplomatic mission.

The ambassador, Viktor Koronelli, immediately informed the Argentine authorities, who seized the cocaine.