Serbian police has arrested 123 people in 18 cities in a major raid carried out in cooperation with Germany, Interior Minister Nebojsa Stefanovic said Tuesday.
They are suspected of a range of acts from the domain of organized crime, including attempted murder, drug production and trafficking, people-smuggling and illegal weapons possession.
Nine police officers were among the suspects, Stefanovic told a press conference.
"Serbia will continue intensive cooperation with Germany in fighting organized crime," he added.
The investigation lasted 13 months. The minister gave no further details on the operation.
Serbia straddles one of the main smuggling routes for heroin from Asia to Europe, with synthetic drugs transported the other way.
It is also on a key migration path, with many migrants having paid gangs to smuggle them from Bulgaria or Macedonia to Hungary in a bid to reach wealthy European countries.