A man accused of having links to an April 27 attack on a police station in Bosnia-Herzegovina's Serb-dominated entity, Republika Srpska, has been arrested there.
Authorities did not detail the suspect's alleged connection to a gunman’s attack on the police post in Zvornik.
But Bosnian Serb Interior Minister Dragan Lukac said the suspect was from Zvornik and “had been previously interrogated in connection with departures to fight in Syria.”
Lulkac also said the man had suspected links to Islamic extremists.
Bosnian media identified the detained suspect as Avdulah Hasanovic.
Bosnian public television said Hasanovic had been in close contact with the 24-year-old gunman, Nerdin Ibric, who was shot dead by police while carrying out the April 27 attack.
Authorities said Ibric entered the Zvornik police station shouting "Allahu Akbar" (God is greater) before shooting dead a police officer and wounded two others before he was killed.
Security Minister Dragan Mektic said the gunman stormed into the building with an automatic rifle and was killed in an exchange of fire with police inside.
Zvornik is located in Bosnia's Serb-dominated autonomous region, the Serb Republic, which together with the Bosniak-Croat federation makes up the Bosnia-Herzegovina that emerged from a 1992-95 war.
"This is the worst terrorist attack that could happen in the Serb Republic," regional Interior Minister Dragan Lukac told local television.
Lukac said that special police forces were sent to the area to help prevent any incidents out of retaliation against Muslims there.
Thousands of Muslim Bosniaks were expelled from Zvornik by Serb forces during the war but some have since returned.
"We shall see if this had been planned or was an individual act," he added.
The imam of the Zvornik mosque, Mustafa Muharemovic, condemned the attack.
Doctors said the police officers' wounds were not life-threatening.
The Bosnian Serb government convened an emergency session and the regional president, Milorad Dodik, told Bosnian Serb TV that he believes the attacker was instructed by someone else, even though he acted alone.