Valentin Krumov had just arrived in Kosovo, one of the legions of U.N. workers come to help rebuild this devastated land. A Bulgarian, Krumov, 38, attracted the attention of a group of ethnic Albanian teenagers as he took an after-dinner walk with two female colleagues along Pristina's crowded main street Monday evening.

Someone speaking Serbian asked him the time, and Krumov replied in Serbian, unaware that he was apparently being put to a kind of ethnic identification test. It was a test he unwittingly failed, and it cost him his life.

The group of young thugs immediately attacked Krumov, punching him and kicking him to the ground. A shot rang out, the crowd fled and Krumov's first night in Pristina ended with his murder -- on Mother Teresa Street.

Bernard Kouchner, the chief of the U.N. mission here, condemned the killing today as "a disgusting and cowardly act," but it was only the latest of hundreds of attacks on Serbs -- and Serbian-speakers -- since the United Nations and NATO peacekeeping troops moved into the Serbian province in June.

Four months after the end of NATO's air campaign and the withdrawal of Serb-led forces, the borders of hate are expanding in Kosovo. The conflict between ethnic Albanians and Serbs is quickly being supplanted by a parallel struggle between forces of tolerance and intolerance within the ethnic Albanian community. So far, intolerance is winning.

"Anyone who thinks that the violence will end once the last Serb has been driven out of Kosovo is living an illusion," Veton Surroi, publisher of the influential ethnic Albanian newspaper Koha Ditore, warned last month. "The violence will simply be redirected against other Albanians."

Krumov, new to this teeming city of swaggering young men and hidden pistols, seemed not to have known that many Slavic internationals, such as Poles, no longer speak their native language here, preferring English or French lest they be mistaken for Serbs. Those Serbs who haven't fled Kosovo have not spoken Serbian on the streets for weeks, because they know the price it could carry.

The return of ethnic Albanian refugees on the back of NATO's victory over Serb-led Yugoslavia unleashed a wave of anti-Serb violence that continues with daily reports of murders and assaults. Recently, for instance, one Serb was killed in a drive-by shooting and two others were stabbed as they worked their fields.

But as the number of Serbs remaining in Kosovo dwindles and those who stay cower in submission, hostility within the ethnic Albanian community -- between those who support creation of a multi-ethnic state and those who oppose it -- is on the rise. It is raising questions about whether the United Nations will ever meet its goal of creating democratic institutions in Kosovo that foster pluralism, free speech, an open economy and widespread participation in the political process.

NATO-led peacekeepers reported last week that three members of the Kosovo Protection Corps, the successor to the Kosovo Liberation Army, were arrested for beating an ethnic Albanian man who had simply purchased a tractor from a Serb. More than a thousand people protested their arrest.

Koha Ditore reported last week that a U.N.-appointed ethnic Albanian management team at a mine near the northern city of Kosovska Mitrovica had its offices trashed by men claiming to represent the self-appointed interim Kosovo government -- formed from the KLA's political wing -- who said they were installing managers loyal to their leaders.

Ethnic Albanians merely suspected of collaboration with the Serbs during NATO's bombing campaign have had their property summarily seized. Some, like one hotel owner in Pristina, have been forced to leave the country under threat of reprisals.

International police, coping with more than 300 unsolved murders, say privately that they receive very little cooperation from the local population when they know there were witnesses to killings such as Krumov's.

"From having been victims of Europe's worst end-of-century persecution," wrote Surroi in his newspaper commentary, "we are ourselves becoming persecutors and have allowed the specter of fascism to reappear. . . . I know the excuses -- that we have been through a barbaric war in which Serbs committed the most heinous crimes; that the intensity of violence has generated a desire for vengeance. This, however, is no justification."

The response to Surroi's plea for pluralism demonstrated the virulence of a smothering orthodoxy here that brooks no criticism.

In an article this month in Kosovapress, the official news agency of the interim government led by former KLA political leader Hashim Thaqi, Surroi and his editor-in-chief, Baton Haxhiu, were described as a "pro-Serb vampires."

The author, heaping the life-threatening charge of collaboration on Surroi and Haxhiu, went on to say that "people like them . . . should themselves realize that, one day, they too may be the targets of some personal vendetta, which is quite understandable. Therefore, both Veton Surroi and Baton Haxhiu, these ordinary Mafiosi, should not be left unpunished for their criminal acts, since their idiosyncrasies deliver water to arch-criminal Milosevic's mill."

The published attack, which was read as a death threat by the United Nations and human rights workers here, drew only the most muted condemnation from the Thaqi government. Kouchner "read the riot act" to Thaqi, Western officials said, and then refused to meet with representatives of his government for a number of days in response.

"We didn't take calls, denied meetings to register our disgust," said one U.N. official.

U.N. officials, however, fear that the article, despite Thaqi's denials, was sanctioned at the highest level of the government. And they therefore feel that it represents a troubling authoritarian streak in the political class emerging from the KLA, which fought a 16-month war for independence against the Yugoslav army and Serbian police and paramilitary forces.

"These guys have no experience with democracy," said one Western official. "They think they have a God-given right to rule because they fought, and the corollary of that is that they think those who didn't fight are unfit."

The tensions between those who fought, or claim to have fought or suffered, and those who didn't is apparent in Pristina, where large numbers of people have flooded in from the battered countryside, bringing with them resentments toward longtime city residents, ridiculed as pampered coffee-drinkers.

"When the Serbs oppressed us, we asked, `Where are the decent Serbs, why don't they speak out?' " said one young Pristina resident. "Now we are afraid to speak out. Things are going wrong and there's a frightening silence."