Portions of southern Yugoslavia have reached such a state of ethnic friction that Yugoslavs have begun to talk of the horrifying possibility of ''civil war'' in a land that lost one-tenth of its population, or 1.7 million people, in World War II.
The current hostilities pit separatist-minded ethnic Albanians against the various Slavic populations of Yugoslavia and occur at all levels of society, from the highest officials to the humblest peasants.
A young Army conscript of ethnic Albanian origin shot up his barracks, killing four sleeping Slavic bunkmates and wounding six others.
The army says it has uncovered hundreds of subversive ethnic Albanian cells in its ranks. Some arsenals have been raided.
Ethnic Albanians in the Government have manipulated public funds and regulations to take over land belonging to Serbs. And politicians have exchanged vicious insults.
Slavic Orthodox churches have been attacked, and flags have been torn down. Wells have been poisoned and crops burned. Slavic boys have been knifed, and some young ethnic Albanians have been told by their elders to rape Serbian girls.
Ethnic Albanians comprise the fastest growing nationality in Yugoslavia and are expected soon to become its third largest, after the Serbs and Croats.
The goal of the radical nationalists among them, one said in an interview, is an ''ethnic Albania that includes western Macedonia, southern Montenegro, part of southern Serbia, Kosovo and Albania itself.'' That includes large chunks of the republics that make up the southern half of Yugoslavia.
Other ethnic Albanian separatists admit to a vision of a greater Albania governed from Pristina in southern Yugoslavia rather than Tirana, the capital of neighboring Albania.
There is no evidence that the hard-line Communist Government in Tirana is giving them material assistance.
The principal battleground is the region called Kosovo, a high plateau ringed by mountains that is somewhat smaller than New Jersey. Ethnic Albanians there make up 85 percent of the population of 1.7 million. The rest are Serbians
Worst Strife in Years
As Slavs flee the protracted violence, Kosovo is becoming what ethnic Albanian nationalists have been demanding for years, and especially strongly since the bloody rioting by ethnic Albanians in Pristina in 1981 - an ''ethnically pure'' Albanian region, a ''Republic of Kosovo'' in all but name.
The violence, a journalist in Kosovo said, is escalating to ''the worst in the last seven years.''
Were the ethnic tensions restricted to Kosovo, Yugoslavia's problems with its Albanian nationals might be more manageable. But some Yugoslavs and some ethnic Albanians believe the struggle has spread far beyond Kosovo. Macedonia, a republic to the south with a population of 1.8 million, has a restive ethnic Albanian minority of 350,000.
''We've already lost western Macedonia to the Albanians,'' said a member of the Yugoslav party presidium, explaining that the ethnic minority had driven the Slavic Macedonians out of the region.
Attacks on Slavs
Last summer, the authorities in Kosovo said they documented 40 ethnic Albanian attacks on Slavs in two months. In the last two years, 320 ethnic Albanians have been sentenced for political crimes, nearly half of them characterized as severe.
In one incident, Fadil Hoxha, once the leading politician of ethnic Albanian origin in Yugoslavia, joked at an official dinner in Prizren last year that Serbian women should be used to satisfy potential ethnic Albanian rapists. After his quip was reported this October, Serbian women in Kosovo protested, and Mr. Hoxha was dismissed from the Communist Party.
As a precaution, the central authorities dispatched 380 riot police officers to the Kosovo region for the first time in four years.
Officials in Belgrade view the ethnic Albanian challenge as imperiling the foundations of the multinational experiment called federal Yugoslavia, which consists of six republics and two provinces.
'Lebanonizing' of Yugoslavia
High-ranking officials have spoken of the ''Lebanonizing'' of their country and have compared its troubles to the strife in Northern Ireland.
Borislav Jovic, a member of the Serbian party's presidency, spoke in an interview of the prospect of ''two Albanias, one north and one south, like divided Germany or Korea,'' and of ''practically the breakup of Yugoslavia.'' He added: ''Time is working against us.''
The federal Secretary for National Defense, Fleet Adm. Branko Mamula, told the army's party organization in September of efforts by ethnic Albanians to subvert the armed forces. ''Between 1981 and 1987 a total of 216 illegal organizations with 1,435 members of Albanian nationality were discovered in the Yugoslav People's Army,'' he said. Admiral Mamula said ethnic Albanian subversives had been preparing for ''killing officers and soldiers, poisoning food and water, sabotage, breaking into weapons arsenals and stealing arms and ammunition, desertion and causing flagrant nationalist incidents in army units.''
Concerns Over Military
Coming three weeks after the ethnic Albanian draftee, Aziz Kelmendi, had slaughtered his Slavic comrades in the barracks at Paracin, the speech struck fear in thousands of families whose sons were about to start their mandatory year of military service.
Because the Albanians have had a relatively high birth rate, one-quarter of the army's 200,000 conscripts this year are ethnic Albanians. Admiral Mamula suggested that 3,792 were potential human timebombs.
He said the army had ''not been provided with details relevant for assessing their behavior.'' But a number of Belgrade politicians said they doubted the Yugoslav armed forces would be used to intervene in Kosovo as they were to quell violent rioting in 1981 in Pristina. They reason that the army leadership is extremely reluctant to become involved in what is, in the first place, a political issue.
Ethnic Albanians already control almost every phase of life in the autonomous province of Kosovo, including the police, judiciary, civil service, schools and factories.
Non-Albanian visitors almost immediately feel the independence - and suspicion - of the ethnic Albanian authorities.
Region's Slavs Lack Strength
While 200,000 Serbs and Montenegrins still live in the province, they are scattered and lack cohesion. In the last seven years, 20,000 of them have fled the province, often leaving behind farmsteads and houses, for the safety of the Slavic north.
Until September, the majority of the Serbian Communist Party leadership pursued a policy of seeking compromise with the Kosovo party hierarchy under its ethnic Albanian leader, Azem Vlasi.
But during a 30-hour session of the Serbian central committee in late September, the Serbian party secretary, Slobodan Milosevic, deposed Dragisa Pavlovic, as head of Belgrade's party organization, the country's largest. Mr. Milosevic accused Mr. Pavlovic of being an appeaser who was soft on Albanian radicals. Mr. Milosevic had courted the Serbian backlash vote with speeches in Kosovo itself calling for ''the policy of the hard hand.''...
Remzi Koljgeci, of the Kosovo party leadership, said in an interview in Pristina that ''relations are cold'' between the ethnic Albanians and Serbs of the province, that there were too many ''people without hope.''...
Efforts are under way to strengthen central authority through amendments to the constitution. ...The hope is that something will be done then to exert the rule of law in Kosovo while drawing ethnic Albanians back into Yugoslavia's mainstream.