30 people were arrested on Tuesday by Serbian and German police on suspicion over drug smuggling. Police also seized narcotics worth around 20 million euros ($22 million), Serbia's interior minister said.
Police seized 303 kg (670 lb) of cocaine, 106 kg of hashish and 96 kg of marijuana as well as weapons and money.
After the 13-months investigation suspects were arrested in Croatia, Germany and Serbia on Tuesday, with 21 others arrested in Spain, Belgium and Hungary between October 2015 and March 2016, Germany's federal police said in a statement. Three further suspects remain at large.
The drug smuggling ring came under suspicion for selling drugs across Europe, German police said. The group had bases in Belgrade and Essen, Germany, with maintaining illegal "indoor plantations"
of marijuana at numerous sites in both countries.
It was the first time the two countries had carried out a joint police investigation, German prosecutor Anette Milk said. "Serbia will continue to cooperate with Germany in all cases related with organized crime and corruption,"
interior minister Nebojsa Stefanovic said.
During the last years Serbia has accumulated its efforts in combating organized crime and corruption. The country lies on key drug-smuggling routes between Central Asia and wealthy European countries, and battling crimes is one of conditions for Serbia to join the European Union.