Serbs Near Takeover of 2nd Bosnia ‘Safe Area’ : Balkans: Zepa’s 16,000 residents hide in cellars, caves. Advancing rebels vow to take all land east of Sarajevo.

The collapse of a second U.N.-protected “safe area” drew closer Sunday as Bosnian Serb infantry, backed by tanks and artillery and ignoring NATO warplanes above, advanced on the heart of the Muslim enclave of Zepa.

Many of the 16,000 Muslim villagers trapped in the mountainous eastern enclave hid in basements or in caves while a small contingent of Bosnian government troops vowed to fight “to the last soldier.”

Most of the 79 Ukrainian U.N. peacekeepers who had been stationed to defend Zepa retreated to a base inside the town after their weapons were seized by government forces.

“They [the Serbs] are in the enclave. They have encroached. They have advanced,” U.N. spokesman Alexander Ivanko said. “The future [of Zepa] is not extremely bright.”

A defiant Bosnian Serb leader Radovan Karadzic served notice that his forces intend to conquer all the land east from Sarajevo, the capital of Bosnia-Herzegovina, to Serbia.

“The Muslim enclaves are not viable and must disappear, or we will do it by force,” Karadzic said in an interview with the Spanish newspaper El Pais.

Relief workers in the Bosnian city of Tuzla began documenting the atrocities suffered by Muslims who were deported from Srebrenica, the first protected enclave to fall to the Serbs. Refugees who fled to Tuzla have reported seeing women taken away by Serbian soldiers, presumably to be raped, and seeing men executed.

“We are facing a genuine case of genocide,” said Emma Bonino, the European Union’s commissioner for humanitarian aid, who was sent to inspect the handling of the refugees in Tuzla--itself another so-called safe area.

Government and relief officials say approximately 23,000 refugees--the vast majority women, children and the elderly--have reached Tuzla after the Serbs expelled them from Srebrenica. An estimated 15,000 people remain unaccounted for, including 4,000 men and boys thought to be held at a soccer stadium in the Serb-held town of Bratunac.

As concern for the fate of the missing grew, the International Committee of the Red Cross ended three days of negotiations with Bosnian Serb political leaders and said the Serbs had agreed “in principle” to grant them access to the detainees. But it would not be immediate access, Red Cross officials said.

A spokesman for Karadzic confirmed that the Serbs are holding an unspecified number of men, whom he characterized as “prisoners of war.” The spokesman, Jovan Zametica, said the men and boys are being investigated to determine whether they have committed crimes against Bosnian Serb civilians. He said the Red Cross would be allowed to visit the detainees soon.

Reporters and relief workers have gathered witness accounts indicating that a considerable number of women and girls were pulled from the buses and trucks that carried the refugees away from Srebrenica. Refugees also said they saw Serbs slitting throats and stabbing several men and boys.

Bosnian Serb commander Gen. Ratko Mladic, an accused war criminal who directed the capture of Srebrenica, had assured the frightened Muslims that they would be treated well and had nothing to fear.

Officials of the Office of the U.N. High Commissioner for Refugees said that, while the reports of atrocities cannot be verified independently, they appear credible and consistent with past behavior by Bosnian Serb soldiers.

As the Serbs threatened Zepa, Bosnian Prime Minister Haris Silajdzic said he feared that the tiny enclave would go the way of Srebrenica. Both, he said, have been betrayed by a United Nations that promised to defend the designated safe areas from Serbian attack and then failed to do so.

The Serbs advanced on Zepa from the south and west, crossing the Rijeka River and entering the enclave as tanks and artillery pummeled the town with heavy mortar fire.

U.N. officials called in North Atlantic Treaty Organization planes to buzz the town, which they did for about two hours. As has become customary, the rebel Serbs ignored the show of force and continued their attack.

Bosnian government officials claimed that Serbian warplanes also joined in the rebel assault and that a Ukrainian commander in Zepa had pleaded for NATO to bomb the advancing Serbs but was turned down. U.N. officials were not available for comment Sunday night.

The move on Zepa came as the senior military officers of the United States, Britain and France convened in London to debate military options for Bosnia. France was expected to promote its plan to use members of a new, well-armed rapid-reaction force to protect Gorazde--like Srebrenica and Zepa an eastern safe area.

Western officials consider Zepa to be a lost cause but may be more willing to make a stand at Gorazde, where 300 British and Ukrainian peacekeepers assist approximately 60,000 residents. The government army there is better equipped than at Srebrenica or Zepa, and a weapons factory is up and running, according to U.N. sources.

Overnight Friday, government troops in Gorazde seized five armored vehicles and other weapons from the Ukrainian post there.

Still, Bosnians remained skeptical that the London meeting or other international diplomatic initiatives would deter the Serbs or slow a war that is rapidly destroying what’s left of Bosnia.

“Experience tells us these consultations are only gaining time for [the Serbs],” Silajdzic told reporters.