The "more than 60 kg (132 pounds) of very pure cocaine" was bound for Turkey, where smugglers planned to pick up heroin for their return, prosecutor Sasa Cadjenovic said at a press conference at the Ministry of Defence in Podgorica.

Police are still looking for two more suspects who are at large, Cadjenovic added.

The naval boat, named Jadran, was searched on Friday by military police shortly before it was set to carry students from the Maritime College of Kotor, a city on the Adriatic coast, on a training cruise to Greece and Turkey.

Montenegro, a tiny Balkan country on the Adriatic coast, has long served as a transit stop for drug trafficking and is considered a hotbed of organised crime.

Defence department representative Colonel Aleksandar Pantovic told the press the military would not allow any "attempts to introduce crime in the ranks of the army."

"There will be no place for such unworthy individuals" to wear the uniform, he added.