BELGRADE, Yugoslavia -- The Yugoslav army went into maximum combat readiness yesterday, mobilizing reserves in Serbia, as local militiamen in breakaway Slovenia persisted in their refusal to allow the army to return to barracks as arranged the night before.
The orders followed a demand by Slovenia's President Milan Kucan that United Nations observers be sent to the breakaway republic to monitor the cease-fire and withdrawal of Yugoslav army units.
Slovenian leaders, whose militiamen have the Yugoslav army pinned down in several locations without communications, electricity or food, have said they fear that the army would use the withdrawal as a ruse to regroup and attack positions in Slovenia again.
The army high command said its troops in Slovenia were being harassed and blockaded by Slovenian forces despite a cease-fire agreed upon Friday.
"The cease-fire will become invalid the moment the lives, health or dignity of Yugoslav People's Army members are endangered in any manner," it said. "The Slovene leadership has been informed that the response to the threat of any such action will be massive and rigorous military attack."
In another development, the army general who commanded the military intervention in Slovenia was fired yesterday. Lt. Gen. Konrad Kolsek, a Slovenian himself, was replaced as commander of the 5th Military District by Lt. Gen. Zivota Avramovic, a Serb, the official Tanjug news agency said, quoting the federal Defense Ministry.
Mr. Kucan's request for U.N. observers was to be raised at a session of the Conference on Security and Cooperation in Europe today in Vienna, Austria. Mr. Kucan said he had accepted a European Community-brokered agreement reached at dawn today.
Earlier yesterday, the foreign ministers of Luxembourg, Italy and the Netherlands left Belgrade after a second visit in 48 hours to persuade the Yugoslavian factions to settle their differences peacefully.
Mr. Kucan said the EC foreign ministers had warned all sides in the conflict that unless they cooperated to make last week's cease-fire agreement work, "we will leave you to your own fate and to war."
The Slovenian leader said he was alarmed because about 200,000 reservists from Serbia and Bosnia and Herzegovina had been called up, an event that was clearly under way in the federal capital here as tanks and soldiers were seen moving through the streets.
"If this mobilization is not halted, a part of the agreement about thewithdrawal of troops to the barracks is not being met," Mr. Kucan said.
Under the terms of a pact mediated by the EC foreign ministers, the two breakaway republics, Slovenia and Croatia, were to suspend for three months their declarations of independence, Yugoslav army troops were to return to their barracks and the republic of Serbia was to stop blocking Croatia's Stipe Mesic from taking over the yearly rotating post of Yugoslav president.
Mr. Mesic assumed the post Sunday night. But yesterday the Slovenians failed to attend a meeting of the collective presidency chaired by the Croatian.
Croatia declared independence from Yugoslavia at the same time as Slovenia did last week. Slovenian President Kucan has in effect accused the Croatians of wanting to keep their cake and eat it by declaring independence on the one hand and accepting the presidency on the other.
While the Slovenian crisis festered on, signs arose of even more widespread unrest in Yugoslavia, what with reservists being called up by the federal army in Serbia, and ethnic and private militias being mobilized in other parts of the country.
Serbia and Croatia, the country's two largest republics, are traditional enemies. More than 700,000 Serbs live on Croatian territory, and they are demanding autonomy for their enclaves with the backing of Serbia. Serb-Croat violence in the enclaves has cost more than 30 lives in the past two months.
The latest upsurge of violence took place in the area of Osijek, in eastern Croatia, where ethnic militias were involved in pitched battles Sunday night.