The five were seized on Thursday in an operation carried out in coordination with Swedish police, Bosnian police spokeswoman Mirna Miljanovic told AFP.
"A huge quantity of arms, ammunitions and military equipment was seized," Miljanovic said, adding that one person was earlier arrested in Sweden, and two others were still at large.
The search was conducted at seven locations in the northern Bosnian towns of Gradiska and Laktasi, he said, giving no further details.
But he said there was no evidence so far that they had links with terrorist groups, and they do not fit a jihadist profile.
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A police source who asked not to be named said however there were some indications the arms were destined for a group called the Muslim Brothers.
The link with Islamists was "not official," the source said, giving no other details of the group, whose name is similar to the Egypt's opposition movement the Muslim Brotherhood.
Local media said the arms included four rocket launchers, 16 hand grenades and one sub machine gun, as well as rifles, pistols and hundreds of rounds of ammunition.