Three months after the war, the dwindling number of Serbs who remain in Kosovo are concentrated in tense enclaves that more and more resemble permanent ghettos.

In these places, the Serbs are watchful and suspicious. As they see it, a flood of hostile ethnic Albanians is set on invading their fragile refuges. Embittered men, some veterans of the province's ethnic conflict, sit at cafes eyeing passersby with suspicion. Ethnic Albanians enter at their own risk.

Outside the Serbian enclaves, the ethnic Albanian Kosovo Liberation Army (KLA), which fought Yugoslav and Serbian security forces during a 16-month war for independence, virtually runs the province as a separate armed force alongside NATO-led peacekeepers and the United Nations. Although the KLA is slated to be demilitarized by Sunday, its leaders plan on pursuing power in Kosovo through involvements in politics, the police and a quasi-military civil defense brigade.

Across Kosovo, every encounter between Serbs and ethnic Albanians, the victims of brutal expulsions by Belgrade security forces during the war, is potentially explosive. In eastern Kosovo, Serbian and ethnic Albanian villages are virtually at war with one another. Drive-by shootings, perpetrated by both communities, are common. Kidnapping makes road travel hazardous, especially for the Serbs.

It is a condition that threatens the professed Western goal of establishing a multi-ethnic society in Kosovo, and even the viability of the NATO-led peacekeeping mission that entered the Serbian province in June after a 78-day allied bombing campaign. The emerging reality is that peace prevails only in areas where Serbs and ethnic Albanians are fully segregated.

This has led some Serbs to suggest that separation, at least for the foreseeable future, is the only way for the groups to live together within Kosovo. "Why try to apply the concept of tolerance to people who are intolerant?" said Dusan Batakovic, a political activist in Belgrade, the Yugoslav and Serbian capital, who has proposed creating five self-governing Serbian districts based on the existing ethnic patchwork.

The United States and NATO have rejected the idea on the grounds that it would effectively seal the province's partition. Ethnic Albanian and Serbian nationalists also have objected to the proposal because each group wants all the territory--for the ethnic Albanians, as an independent Kosovo; for the Serbs, as part of Serb-dominated Yugoslavia.

Even so, Kosovo is already divided along deep ethnic lines. In town after town, Serbs have fled their homes and been expelled from hospitals, factories, mines, schools and other public facilities in ethnic Albanian-controlled areas. Albanians are barred from such places that exist in Serb enclaves.

In the northern city of Kosovska Mitrovica, fear and hostility have produced a dangerous standoff. Serbs have blocked a bridge over the Ibar River that divides the city in half--one section almost exclusively Serbian, the other ethnic Albanian. Efforts by irate ethnic Albanian youths to storm the Serbian enclave turned violent last week for the third time since NATO peacekeepers occupied Mitrovica in June. Stone throwing and gunfire wounded dozens on both sides, and French troops patrolling the banks were hit by rocks and shrapnel from a grenade.

"Our situation is bad," said Oliver Ivanovic, a former policeman and karate teacher who heads a Belgrade-approved council of Serbs in Mitrovica that acts as a local government. "Our relations with Albanians can't be fixed, even if we had contact. NATO thinks it has the power to fix it, but first, everyone needs protection, and they can't provide that."

International observers estimate the number of Serbs in Kosovo at 97,000, about half the prewar population, when Serbs accounted for approximately 10 percent of the province's 1.8 million inhabitants. Some estimates put the current number as low as 50,000.

Serbs are mainly concentrated in Kosovska Mitrovica; in villages to the north, closer to the border with Serbia proper; in and around Kosovo Polje and Gracanica south of Pristina, the provincial capital; in the east around the town of Gnjilane; and in the town of Strpce near the Macedonian border.

Before the war, Pristina was home to about 30,000 Serbs. That population has shrunk to less than 2,000. Serbian apartment houses there have become tense islands of fear. Scattered Serbian high-rises are under 24-hour a day guard by U.N. police and NATO troops. Empty Serbian apartments are frequently raided and occupied by homeless ethnic Albanians. No one dares leave common entrances open, for fear that someone will lay a bomb on a staircase. Last week, one blew up, killing a Serbian man. Shoppers sometimes travel as far as Gracanica--about 10 miles away--rather than risk venturing onto Pristina's streets.

Mitrovica, a drab, gray mining and industrial town, has become a symbol of Serbian resistance. For fear of clashes, NATO tolerated the division of the city. French troops occasionally escort ethnic Albanians into the district to inspect homes they abandoned when forced into exile during the war.

At the Dolce Vita Cafe on the Serbian side of the bridge, men with time on their hands pass the days sipping beer and looking out the corner of their eyes across the river. They refer to the Albanians as "hordes."

"Do you think we could cross over there?" asked one. "An individual Albanian can come--you see, there goes one--but not the hordes."

Said another: "NATO wants to make us like American Indians in reservations."

Serbian refugees from other parts of Kosovo occupy apartments in Mitrovica abandoned by ethnic Albanians. One such occupant is Jelena Mitrovic, a homemaker who fled Vucitrn, a town 15 miles to the southeast, when ethnic Albanians burned her house down. She said she spends her days visiting acquaintances from her hometown. "What is there to do? We don't even have a movie theater here," she said. "I can't go to Pristina. The Albanians would eat me alive."

Elsewhere in the province, dozens of kidnappings have made Serbs wary of travel. Two weeks ago in Gracanica, Serbs blocked the main road from Pristina to Gnjilane to protest a kidnapping. The man had driven to the countryside to collect firewood. He was the fourth kidnap victim from the town.

NATO troops permitted the blockade, in part because other roads to Gnjilane are still open. The peacekeepers also fear riots and attacks on ethnic Albanians who might use the road.

At an open-air town meeting, the local British commander, Col. Bill Cubitt, tried to defuse tensions over the kidnapping. He announced that NATO was working with the KLA to resolve the case. The crowd howled. "Why not arrest the KLA? They're responsible," shouted one spectator.

Perhaps the most forlorn of Serbian ghettos lies inside Orahovac, a town in southwestern Kosovo dominated by ethnic Albanians who were expelled to Albania during the war. About 3,000 Serbs remain, because their escape routes passed through ethnic Albanian towns and villages, where they feared the rage of returned refugees.

Now they are further cut off from the world by an ethnic Albanian protest against a NATO decision to dispatch Russian peacekeepers to protect the Serbs in Orahovac. The KLA, which accuses the Russians of a pro-Serb bias, organized a blockade of two entrances to the town with trucks, tractors and barbed wire. Outsiders must take a mile detour to get in after passing through KLA document inspection. The KLA has refused repeated NATO requests to lift the blockade.

The Serbs live on a steep hillside, overlooking their shops and homes that have been sacked and burned in retaliation for the torching and smashing of Albanian property during the war. Even if the Russians arrive, most of the Serbs say they will not stay. "Once we leave, we'll never come back. That's the way it is in the Balkans," said Lyubomir Labovic, a farmer who took refuge in Orahovac from an outlying village.

The Serbs produced an exhibit to explain the terror they feel: Milica Grkovic, a widow who said her husband was scalped and killed in June by vengeful ethnic Albanians. Said Sveta Jovicic, a retiree: "Tell someone to come get us out of here."