Casualties Rise in Unraveling Yugoslavia : Ethnic strife: The presidency again urges a cease-fire--with little visible effect.

Armed exchanges between Croatian separatists, Serbian militants and an increasingly tough-minded Yugoslav federal army kept the casualty toll slowly but steadily mounting Friday, while the unraveling nation’s leaders met--still without much visible effect--to avert further bloodshed.

Yugoslavia’s collective federal presidency met all day Friday in Belgrade and called for a cease-fire on all sides, warning that the “situation threatens to deteriorate into total war.” But there was no indication that the eight-man presidency, called into session by Stipe Mesic, Croatia’s representative to the group and its current chairman, had come near any solution for reducing the tension in breakaway Croatia, which along with Slovenia announced its intention to secede from the Yugoslav federation on June 25.

In the past week, 49 Croatian police and national guard reservists, part of a poorly organized attempt at a Croatian national army, have died in clashes with Serbian militants or in exchanges of fire with the federal army, positioned at key bridges and crossing points into the republic.

Twenty were killed in fighting in Croatia on Thursday, primarily in clashes between Croatian militiamen and the federal army. The army, which Croatian separatists say is dominated by Serbs hostile to the secession ambitions of the republic, has warned Croatian fighters that it will open up with force if its units are fired on. This week, commanders of units in the area say, it has followed through on its warning.

With the situation increasingly stalemated and dangerous, diplomats say Croatian leaders are talking even more militantly, evidently with the hope that fear of all-out war will lead to an intercession by the international community and thus lead to a European-brokered independence for the republic.

It was international alarm, in part, that forced the central government to take steps that may allow Slovenia, the other breakaway republic, to achieve full independence. Slovenia, for the first time since its independence declaration, opened its airports Friday.

Croatia is finding the road to independence far tougher. Its move is opposed by the other republics--Serbia foremost among them, since there are 600,000 ethnic Serbs living in Croatia. Fighting between the ethnic Serbs and the Croats has accounted for most of the casualties in Croatia, but the role of the federal army appears to be growing in importance.

The Croatian government Friday accused the army of “brutally attacking the territory of Croatia” and of adopting a policy of “increasingly open aggression in which many lives of Croatian citizens have already been lost.” It demanded that the army return to its barracks or “we shall view it as an army of occupation whose sole aim is to destroy the lives of the Croatian population, seize Croatian territories and overthrow the legitimate Croatian authorities.”

The rhetoric is even harsher among Croatia’s militia leaders. After two Croatian guardsmen were killed and six wounded in a clash with Serb militants near Vukovar in the Slavonia region of eastern Croatia, Ivan Cvitkovic, a unit commander, told Tanjug, the Yugoslav news agency: “Words have been exhausted. It’s time for fighting.”

The tension is disrupting lives throughout the region. The federal minister of health and social services, Radisa Gasic, said Friday that 44,316 Yugoslavs had registered as refugees from the sporadic fighting.

In other clashes Friday, a Croatian policemen was killed in an ambush near the town of Otocac, in western Croatia, according to Zagreb radio. The radio also reported skirmishes around the Serbian-dominated town of Brsadin, with dead and wounded on both sides, although no casualty figures were given.

One man was reported wounded in a mortar attack in the town of Glina, 30 miles south of Zagreb. Milan Brezak, Croatia’s deputy interior minister, said that more than 80 mortar shells were fired at Glina from nearby Serb-populated villages, most of them aimed at Glina’s police station, one of the few buildings still in Croatian hands in the largely Serbian town.