Croats Herd Muslims to Camps, U.N. Aides Say : Bosnia: Battle in Mostar confronts Sarajevo with a 2-front war. Gunmen deny entry to U.N. commander.

Bosnian Croat nationalists have herded as many as 2,500 Muslims into makeshift detention camps near the embattled southern city of Mostar, separating families and exposing the civilian prisoners to deprivation and disease, U.N. sources reported Wednesday.

Croatian gunmen also blocked the commander of U.N. forces in Bosnia-Herzegovina, French Gen. Philippe Morillon, from entering Mostar on a mission to seek peace between the former allies.

Croats have lately been fighting Bosnia’s Muslims with more ferocity than the Serbian rebels who have besieged the republic for more than a year. A month of clashes between Croatian militia forces, called the HVO, and Bosnian government troops have killed hundreds and confronted the already overwhelmed Sarajevo leadership with a two-front war.

U.N. troops trying to gain access to Mostar since a Croatian offensive began at dawn Sunday managed to visit an idled factory where Muslims were being held and determined that they had been driven from their homes at gunpoint, said a spokesman for the U.N. Protection Force in this Yugoslav capital.

“Somewhere between 1,300 and 2,500 civilians are being held in a helicopter factory and two gymnasiums,” he said. “So far there have been no signs of harassment, but conditions are not terribly good and they are worsening by the minute as more (prisoners) are being brought in.”

He said Muslim men were being separated from their wives and children and held in another facility.

Aid officials warned that the latest victims of “ethnic cleansing” risked contracting diseases because the places of detention lack adequate water and toilets.

Morillon traveled to Mostar intent on brokering a durable cease-fire but was turned away by HVO gunmen, the U.N. spokesman said.

Mostar, home to 125,000 before the war, was a largely Muslim tourist haven along the teal-blue Neretva River, which Serbs and Croats regard as the natural boundary dividing their respective Orthodox and Catholic communities.

Bosnian government leaders contend that the recent fighting is the result of a conspiracy between Belgrade and Zagreb to divide Bosnian territory between them and drive out the Muslim Slavs, who were Bosnia’s largest population group.

The U.N. high commissioner for refugees’ special envoy to the former Yugoslav federation, Jose Maria Mendiluce, warned that the Croatian action in Mostar could worsen the already catastrophic problem of more than 2 million people cast out of their homes by the Bosnian war.

“If things do not stop immediately . . . it could lead to a massive movement of 200,000 or even 300,000 people,” Mendiluce said, noting that Muslims living in areas designated for Croatian control under a Western-mediated peace plan are increasingly fearful of falling under extremist rule.

U.N. envoy Cyrus R. Vance and Lord Owen of the European Community have proposed dividing Bosnia into 10 ethnic provinces, with three each to be governed by Muslims, Serbs and Croats and the tenth, around the capital of Sarajevo, to be jointly administered.

Most of the recent Croat-Muslim fighting, which U.N. officials say was instigated by the HVO, has taken place in predominantly Muslim communities destined for Croatian control. At least 250 were killed in the clashes last month, and Bosnian Radio reported dozens of corpses strewn over Mostar streets in the past three days.

Several European governments have warned Croatian leaders in Zagreb--believed to be tolerating, if not encouraging, the Bosnian Croat aggression--that relations with Western countries could suffer if the violence continues.

“The Croatians should have no doubt that if this kind of incident which has occurred in central Bosnia and has now again occurred in Mostar continues, then they cannot expect to have the kind of relations with the EC or the international community which they have expected,” British Foreign Secretary Douglas Hurd warned during an address to Parliament.

Russian and German leaders have also brought their concerns about the recent bloodshed to the attention of Croatian President Franjo Tudjman.

In eastern Bosnia, where Serb guerrillas have overrun all but three towns, U.N. forces evacuated 37 injured Muslims from the holdout enclave of Zepa.

But the airlift was delayed by several hours when Serbian gunmen objected to the presence of a Muslim doctor aboard one of the helicopters.

Although Zepa and five other towns still populated by Muslims have been declared U.N.-protected areas, conditions in the purported “safe areas” remain primitive, U.N. refugee officials say.