PEC, Yugoslavia (AP) _ Thousands of Serbs, many weeping, gathered today to mourn six slain countrymen whose deaths have inflamed tensions in the separatist province of Kosovo.

A crowd of 5,000 assembled in the western city of Pec, where unknown assailants on Monday opened fire in a Serb-run bar. Another 2,000 to 3,000 Serbs attended a protest rally today in the provincial capital of Pristina.

Despite fears of unrest, the gatherings were peaceful, with four busloads of Serb police providing security in Pec. International monitors were not in evidence, a day after some Serbs took out their anger at the killings by hurling stones or spitting at armored U.S. observer vehicles.

As mourners sobbed, the six coffins were brought to Pec's main square and covered with wreaths. The victims were buried later in the day.

``Pain and sorrow is in our hearts,'' said Mirko Simonovic, principal of the high school where four of the dead were students.

``They were killed for the simple reason of being Serbs.''

He concluded with a demand that the state ``punish the perpetrators and do away forever with Albanian terrorism.''

Serbs blame ethnic Albanian rebels for the killings, which have prompted protests and threats of retaliation.

Many fear the killings, along with a border clash this week between the Yugoslav army and ethnic Albanian rebels that killed at least 36 rebels, move Kosovo closer to a renewal of war.

Ethnic Albanians make up 90 percent of the population of Kosovo, a province of Yugoslavia's main republic of Serbia.

Voicing concern at the dangerous turn of events, U.S. envoy Richard Holbrooke condemned the deaths as ``appalling beyond words.''

Yugoslav President Slobodan Milosevic renewed his determination to suppress rebel ``terrorism.'' A top government body for the Serbian province said the Serb killings were ``the most monstrous crime in the series of assaults by Albanian terrorist gangs.''

Holbrooke, who brokered an agreement in October that halted more than seven months of combat in Kosovo, appeared pessimistic about reaching a political settlement that could stop the carnage.

After more than five hours of talks with Milosevic in Belgrade, Holbrooke acknowledged Tuesday night that diplomats are nowhere near bridging the huge divide between Serbs and Kosovo's ethic Albanians on the province's status.

Pec, 45 miles west of Pristina, is Kosovo's third-largest city with about 150,000 residents. Like Kosovo itself, the population is overwhelmingly ethnic Albanian, but several thousand Serbs also live there.

Towns and cities have mostly escaped the violence that has engulfed Kosovo villages this year since the Serb assault on militant separatists that began in February.

More than 1,000 people have been killed and 300,000 forced from their homes.