They added that the intended victims came from four small towns in the Bihac area of northern Bosnia-Herzegovina, a region surrounded by Serbian forces determined to evict non-Serbs to 'purify' the area.
As in earlier mass expulsions, the Bosnian Serb authorities have, in effect, tried to blackmail the UN and Croatian government into accepting the uprooted Muslims by hinting that an even worse fate may befall them if they stay.
Less than a month ago, Croatia was forced to take up to 14,000 refugees from the border town of Bosanski Novi, after Bosnian Serbs suggested they could not guarantee their safety.
About 5,000 of those refugees were moved quickly to Germany. The total number of refugees within and outside the former Yugoslavia is more than 2.2 million, including more than one in three of Bosnia's population.
UN officials say the Serbs have trapped them in a morally impossible position. 'If we help the people out, we are helping (the Serbs) cleanse the areas. If we don't help them leave, there is a very difficult situation,' said Jose Maria Mendiluce, special envoy of the UN High Commissioner for Refugees.
Conscious that their international image needs improving, the Bosnian Serb leaders in Sarajevo have signed an agreement with UN peace-keepers under which women and children are to be moved out in protected convoys.
The operation is scheduled to begin today, partly because the UN emergency relief programme has been unable to provide enough food and medicines for people trapped in the besieged city. The UN has flown supplies into Sarajevo for the past six weeks, but the airlift brings in no more than 200 tons a day, far less than is needed.
There were conflicting reports yesterday on the exact number and whereabouts of the Muslims about to be deported to Croatia. One UNHCR official in Zagreb, Peter Kessler, said there were about 20,000, many already close to the Bosnian-Croatian border.
But Lars Nielsen, field co-ordinator in the former Yugoslavia, estimated the number at 28,000. He said some had been 'collected in large groups' by the Serbs, while others were still in their homes.
As in the past, the Muslims are being forced to sign away their property before receiving orders to leave. Since the Bosnian war broke out in April, many thousands of Muslims have been held in detention camps after being forced out of their homes.
Mr Nielsen said he had calculated the number of refugees from information from local authorities, as well as from Bosnians who had said they wanted to leave.Reuse content