Britain accused the Yugoslav leader, Slobodan Milosevic, of plotting to topple the government of Milo Djukanovic, which has refused to declare a state of war in the republic, or even to denounce Western air strikes with much conviction.
"We have evidence to show that he is preparing a coup against Montenegro," a Ministry of Defence official, Edgar Buckley, said in London.
In the Montenegrin capital, Podgorica, the government appealed for calm. "There is no reason to panic," Predrag Drecun, a government minister, said.
But many disagree. Their fears have been stoked by President Milosevic's decision on Thursday to fire General Radosav Martinovic, the army commander in Montenegro, and replace him as head of the 2nd Army with Milorad Obradovic, a trusted hardliner who can be relied on to follow Belgrade's orders.
"These moves must be recognised for what they are - a plot to dislodge an elected government," Mr Buckley said. "We shall be watching the situation very carefully."
Montenegro has infuriated Serbia, its bigger partner in the Yugoslav Federation, by seeking closer ties to the West, refusing to endorse the hate campaign against ethnic Albanians. For months, it has also publicly floated plans to secede from Yugoslavia. If Montenegro leaves, Yugoslavia would consist only of Serbia. Until 1991, Yugoslavia comprised six republics.
A Serbian coup would strike terror into the 30,000 Albanians who have fled to Montenegro from Mr Milosevic's army, paramilitary police and death squads in Kosovo. "If those butchers from Kosovo come here, we are in trouble," said one senior Montenegrin politician.
Ferhat Dinosa, a leader of the local Albanian party in Montenegro, tried to put an optimistic gloss on the coup rumours. "Milosevic will try to gain control. But everyone here has seen what happened in Bosnia and what is happening in Kosovo," he said.
There are suspicions that the flood of Albanian refugees into Montenegro may help to serve Mr Milosevic's purposes in the republic by upsetting the fragile ethnic balance.
Until last week, Albanians made up only 6 per cent of the 600,000 population but the flow of refugees is altering that percentage every day.
Serbia already has many supporters in the republic. The main opposition party, the Socialist People's party, is vehemently pro-Milosevic and bitterly opposes talk of secession and the present government's pro-Western tilt.
The United States has warned that any attempt to undermine Montenegro's government could extend the conflict with Nato.Reuse content