Bosnian authorities have identified two suspects arrested in connection with a fatal attack on a police station, including one already under investigation for allegedly helping to recruit fighters for the Islamic State group.

Monday's attack in the Bosnian Serb town of Zvornik left a Serb policeman and a Muslim gunman dead and two officers wounded, raising tensions among Bosnia's ethnic groups.

Prosecutors identified the two suspects on Thursday as 24-year-old Avdulah Hasanovic, and 40-year-old Kasim Mehidic.

Hasanovic was detained last year in a sweep against Islamic extremists who were allegedly recruiting people to fight for IS in Syria. Hasanovic was later released as part of that investigation, but his passport has been confiscated and he has had to regularly report to authorities. The group's leader is on trial.