BANJA LUKA, Bosnia-Herzegovina (AP) – Angered by plans to rebuild a mosque in their city, a Bosnian Serb mob beat dozens of Muslims and forced U.N. and other Western officials to take refuge Monday inside Banja Luka’s Islamic center.

More than 1,000 Serbs broke through a cordon of police and attacked participants in a ceremony in Banja Luka launching the reconstruction of a mosque razed by Serbs in 1993.

Black smoke from five burning buses and a car rose high into the sky, and a bakery was set afire as protesters chanted, ”This is Serbia,” and ”We don’t want a mosque.”

The Serbs beat visitors and set Muslims’ prayer rugs on fire. One man was left lying on his prayer rug, his face bloodied. To insult the Muslims, the Serbs chased a pig on the site where the mosque stood.

They then climbed atop the Islamic center, burned a flag there and hoisted the Bosnian Serb flag. About 250 Muslims were trapped in the building – along with the head of the United Nations in Bosnia, Jacques Klein, the British, Swedish and Pakistani ambassadors, as well as other high-ranking international and local officials attending the ceremony.

Several hours later, Bosnian Serb police stepped in, forming and barrier and evacuating those trapped in the building. U.N. spokesman Fred Eckhard in New York later said all had been brought out safely.

”There are a few people hurt from thrown rocks, with bloody foreheads, broken skin,” Klein, a U.S. citizen, said by phone while still trapped in the building. Banja Luka police chief Vladimir Tutus said 18 Muslims were injured along with 24 Serbs, including 11 of his men.

Reports that at least one person died after being trapped in the burning bakery could not be confirmed either by local or international officials.

The 16th-century Ferhadija mosque was leveled by the Serbs along with all the other mosques in Banja Luka after Muslims were expelled from the city early in the 1992-1995.

Banja Luka is now the main city in the Serb half of Bosnia. The 1995 peace accords left Bosnia formally one nation, but split it into a Serb half and another shared by Croats and Muslims.

Around 1,000 Muslims who had lived in Banja Luka were bused in for Monday’s ceremony. Bosnian Serb leaders had grudgingly agreed to the reconstruction – part of international officials’ efforts to return refugees to their homes across the country.

Before the ceremony, the Serb protesters gathered across the street from the site, blasting nationalistic songs and throwing stones, eggs and firecrackers over the heads of police. They chanted the name ”Radovan Karadzic” – the Bosnian Serbs’ wartime leader who is the country’s most wanted war crimes suspect.

One stone smashed through a car windshield and struck Bosnia’s foreign minister, Zlatko Lagumdzija, in the head. He said he was not injured.

Tutus told reporters his officers moved in to evacuate the trapped people after NATO-led peacekeepers threatened to intervene.

Wolfgang Petritsch, the chief international administrator of Bosnia, criticized Bosnian Serb authorities for permitting extremists to ”spread ultranationalism, intolerance and violence.” U.S. Ambassador Thomas Miller said the ceremony ”should have been a symbol of peace and reconciliation.”

Klein said the mob was well organized. ”You don’t get that many people into a square without some organization and structural arrangement,” he said.

A similar mosque reconstruction ceremony Saturday in the southeastern town of Trebinje also was disrupted by Serb nationalists. Several visitors were injured, including Daniel Ruiz, the local representative of Bosnia’s top international official.

In Sarajevo, Zivko Radisic, the Serb member of Bosnia’s multi-ethnic collective presidency, condemned the attack ”against national and religious tolerance.” Bosnian Serb police minister Perica Bundalo and Tutus offered their resignations, and local and government authorities were to decide Tuesday whether to accept them.