"A certain quantity of arms was found, as well as grenades, ammunition, automatic rifle magazines, knives, combat vests and flags looking like Islamic State insignia," a prosecutors' statement said.

It did not elaborate whether the suspects planned to commit terrorist acts.

Their age or identity was also not revealed.

In December, a 25-year-old Bosnian man, in possession of a large quantity of weapons, was arrested in Sarajevo.

He had already been sentenced in 2016 to a year in prison for having joined the ranks of the Islamic State group in Syria in 2013.

The man was arrested at Sarajevo's bus station, not far from the US embassy.

In the boot of his car, police found a rocket-launcher, two automatic rifles, a large amount of ammunition, an anti-personnel mine, four grenades and two combat vests.

About 1,000 people from the Balkans joined jihadist ranks to fight in Syria and Iraq since 2012 but the flow has dried up, with more than 200 killed on the frontline.

Another 300 or so have returned to the Balkan region.

Interpol is currently searching for some 20 Bosnian citizens suspected of terrorism, the Dnevni Avaz daily paper reported Tuesday.