An international police operation coordinated from Croatia has broken up a "highly violent" criminal gang from the Western Balkans and arrested 37 people, Europol said Thursday.

The "powerful criminal cell" was mainly involved in the large-scale trafficking of drugs and firearms across Europe, the European Union law enforcement agency said.

"A total of 37 suspects were arrested over the course of the investigation, including the gang’s ringleader - a national from Bosnia and Herzegovina considered as a high-value target by Europol and currently serving a four-year-long prison sentence in Italy," Europol said in a statement.

The gang leader is suspected of having orchestrated the trafficking of drugs and firearms by giving orders to his subordinates from behind bars, Europol added.

On Thursday, a series of raids were carried out simultaneously across Croatia, Slovenia, Bosnia and Herzegovina, the Netherlands, Italy, Belgium and Germany against suspected members of the gang.

Along with the arrests, police seized some €148,000 in cash, 18 firearms including two machine guns and 500 grams of TNT with remote detonators.

Police also seized 15 kilos of cocaine, 11 kilos of heroin as well as quantities of amphetamine, marijuana and hashish.

The international sweep followed what Europol described as a "complex investigation" led by Croatian police as part of the "Balkan Cartel" Operational Taskforce.