PAKRAC, Croatia -- Croatian radio said rebel Serbs, who defied cease-fire orders after Croatian troops overran a separatist pocket, surrendered Thursday after a ferocious firefight in the divided town of Pakrac.


"They have accepted a Croatian government appeal and a large number of Serbs have crossed over to the free territory of Croatia," the state radio said. It was not immediately possible to verify the report.


HINA, the state news agency, said intense artillery and mortar battles between about 200 die-hard Serb militiamen holed up in the hilly part of Pakrac and Croatian troops in the town stopped at around 4 p.m.


Croatian security forces then crossed the UN peacekeepers' checkpoint into what had been the Serb-held district of the town, in the Western Slavonia region 100 kilometers east of Zagreb, HINA reported.


Thousands of Croatian troops with tanks seized virtually all of Western Slavonia in a 31-hour surprise attack over United Nations cease-fire lines earlier this week.


Most of the separatist Krajina Serb forces who had held the region for four years fled across into neighboring Bosnia. Some 400 others surrounded in the Pakrac region agreed to surrender under UN protection, but 200 from the same unit retreated to woods above the town and kept fighting.


Despite reports of surrender, Serb hard-liners from Bosnia and Croatia threatened to retake territory lost to the Croatian army unless the UN restored Serb control over the area and Croats returned to their original positions.


Bosnian Serb leader Radovan Karadzic and two of his senior associates met Milan Martic, the ultranationalist rebel Serb leader in Croatia, in his Knin stronghold to discuss Croat gains. A statement from the joint Bosnian Serb and Croatian Serb military command said the UN Security Council had "an obligation to the world community to secure the liberation of the occupied Serb population and the return of the Croatian army to its original positions."


As the fighting was raging in Western Slavonia, warning sirens sent Zagreb residents rushing for shelters Thursday for the third time in as many days. Six people died and 185 people were wounded in two consecutive rocket attacks Tuesday and Wednesday, unleashed by rebel Serbs smarting under the government army offensive.


Parliament cut short its special session Thursday, and legislators and others sought out basements and other protected areas. But there were no reports of detonations, and an all-clear was sounded less than an hour later.


Tensions also rose to the southwest, where the UN said close to 1,000 Croatian soldiers and up to seven tanks moved into a 50-kilometer stretch of buffer zone separating the warring sides between the towns of Otocac and Gospic. Otocac is 60 kilometers northwest of the Croatian Serb stronghold of Knin and Gospic only 40 kilometers away.


Edgy Serbs fired toward the Croatians in at least one instance, damaging a UN vehicle but causing no casualties. But Yury Shishayev, a UN spokesman, said there were "reasons for concern'' with additional Croatian troops moving into the zone. (Reuters, AP)