Bosnian Serb police clashed with nationalist rioters Monday, using tear gas and water cannons to beat back mobs trying to disrupt a ceremony to mark the rebuilding of a medieval mosque.
Hundreds of Bosnian Serbs in this northern city attacked police with stones and bottles, injuring 13 officers, one of them seriously, local police chief Drago Gacesa told reporters.
About 60 protesters were detained after several hours of trouble, police said.
The demonstrators, angered at Western-backed efforts to re-integrate Bosnian Muslims driven out during the 1992-95 war, shouted anti-Muslim slogans and sang nationalist songs but failed to stop the ceremony.
It was the second time violence has marred efforts to formally mark the reestablishment of Muslim religious life in the "capital" of the half of Bosnia now controlled by Orthodox Christian Serbs.
Riots a month ago killed a Muslim man and forced the postponement of the cornerstone ceremony for rebuilding the 16th century Ferhadija mosque, which was destroyed by Serbian extremists in 1993 during campaigns to expel local Muslims.
That outburst of chauvinism brought fierce condemnation from the Western overseers of the Dayton peace deal, which ended the war in 1995. The riots underlined the difficulty of damping down the extreme nationalism that divides Bosnia's ethnic groups.
Bosnian Serb Vice President Dragan Cavic said he regretted the violence. The police response was "aimed at showing that the Serb Republic was ready to use legal means to provide normal functioning of society," he said.
If rioters had prevented the ceremony again, "it would have negative consequences for the Serb Republic and its future," he said, referring to Western sanctions against Serbian parties that back extremists.
Three top Bosnian Serb Interior Ministry officials were fired after May's riots in northwestern Banja Luka and in the southern town of Trebinje, where a similar mosque reconstruction was blocked by violent Serbian nationalists two days earlier.
A tight security cordon allowed Muslim clerics, Bosnian officials and Western diplomats to proceed with the rebuilding ceremony Monday.
"Let this mosque be a bridge of reconciliation between Muslims and Christians," the head of Bosnia's Islamic community, Mustafa Ceric, said at the ceremony.
Mirko Sarovic, the nationalist president of the Bosnian Serb republic, which together with the Muslim-Croat Federation makes up Bosnia, participated in the ceremony.
He had refused to attend last month.
Western peace overseers welcomed Sarovic's presence and the robust police response to the violence.
"We hope that now more will be done on improving human rights in order that refugees could go back to their prewar homes," said Sonja Pastuovic, a spokeswoman for the Banja Luka regional office of the West's high representative in Bosnia.
Banja Luka was the second-largest Bosnian town before the war, but most members of its large Muslim population either fled or were expelled early in the war.
All 15 mosques in the town itself and 90 in the area were blown up.
A total of 618 mosques throughout Bosnia were destroyed during the bloody ethnic conflict that left as many as 200,000 people dead.