Nato-led peacekeeping troops in Bosnia said yesterday they were on guard against possible reaction to any NATO bombing of Yugoslav targets.
Lieut Cmdr Glenn Chamberlain, spokesman for the international peacekeeping force, reiterated that it would not back away from any necessary action to prevent the Kosovo crisis from spilling over into Bosnia.
The NATO-led Stabilisation Force (SFOR), whose 32,000 troops help secure peace between Bosnia's Serbs, Croats and Muslims, had so far not observed any "significant activities" as a result of Western threats to bomb Yugoslavia.
But he also said that SFOR had no reason to doubt media reports that some soldiers from Yugoslavia, whose dominant republic is Serbia, had been seen moving across the border with Bosnia's Serb Republic.
SFOR patrols routinely monitored the situation.
Recent remarks by the Serbian Deputy Prime Minister, Mr Vojislav Seselj, implied there would be retaliation against the peace force in Bosnia if NATO bombed Yugoslavia, and a Bosnian Serb leader said that such strikes would represent an attack on all Serbs.
The US-brokered Dayton peace accord bans any co-operation between Yugoslav and Bosnian Serb forces.
According to reports from Belgrade, Muslim families were yesterday leaving Serbia's Sandzak area for fear of reprisals if NATO carries out air strikes.
Sandzak lies to the north of Kosovo and also borders Montenegro, the other republic making up Yugoslavia.
Many Muslim families were leaving Serbia and fleeing to Bosnia, hoping to find refuge in Sarajevo.
The head of the local Helsinki Committee of Human Rights in Sandzak, Mr Sefko Alomerovic, said the Yugoslav army had deployed artillery in the hills around Novi Pazar, the main city in the Sandzak region, and reinforced troops and police. In a telephone interview from Novi Pazar he said Muslims were alarmed by the physical appearance of some police.
"The way they look and behave shows that not all of them are professionals," he said. "This scares people, prompting many families to leave for Bosnia, but also for Western countries." Mr Rasim Ljajic, a Sandzak Muslim political leader, said up to 17 families a day were known to be leaving but that the true size of the exodus was difficult to estimate.