Seven Colombian nationals suspected of acting as enforcers for drug cartels were arrested in Madrid in possession of a grenade-launcher and other armament, Spanish officials said Monday.

Authorities had been tracking the suspects for 16 months and decided to pounce after the group received a shipment of weapons, the secretary of state for Security, Francisco Martinez, and police director Ignacio Cosido told a press conference.

Besides the grenade-launcher, the consignment included a rifle with a telescopic sight, handguns, shotguns and silencers.

Investigators think the suspects were sent to Spain to collect debts and settle scores on behalf of Colombian drug cartels while also trying to forge an alliance with Mexican traffickers based in the Mediterranean city of Valencia.

The seven Colombians operated from a restaurant in the Madrid suburb of Leganes and used the phrase "to send flowers" as code for a hit, police said. EFE