Bosnia is mourning a policeman who was killed in what authorities are treating as a terrorist act committed by a Muslim gunman in the northeast of the country.

Flags are at half-mast on Wednesday as policeman Dragan Djuric is being laid to rest, while authorities in Bosnia have vowed to strengthen the fight against terrorism.

Monday's attack in the Bosnian Serb town of Zvornik left the Serb policeman and the gunman dead and two officers wounded. Prosecutors suspect Islamic terrorism but authorities have called for patience until the investigation is over. Police arrested two men allegedly connected to the gunman.

Security Minister Dragan Mektic said Bosnia must launch an unrelenting fight against terrorism and investigate any flaws in its security system.