Secretary of State Madeleine K. Albright received a rapturous reception from Kosovo Albanians here today, but a U.S. official said she cautioned Kosovo Liberation Army leaders that they are moving too quickly to assert control over the battered Serbian province.

Albright's warning echoed a sense among some foreign officials here that the KLA--an ethnic Albanian militia that fought for independence from Serbia--is exploiting U.N. difficulties in establishing international rule here and is creating an unofficial government that will be hard to displace.

The KLA has occupied state property, appointed officials, begun exercising local governmental authority and sanctioned expropriation of Serbian property, according to U.N. officials. The U.N. response, particularly outside Pristina, the provincial capital, has been ineffective, U.N. officials acknowledge.

In addition, Albright's one-day visit here came as the province's dwindling Serbian population is feeling particularly threatened by the ethnic Albanian majority following the massacre last Friday of 14 Serbian farmers and the burning of a number of Serb-owned houses since NATO troops occupied the province seven weeks ago. Kosovo's prewar Serbian population of 200,000 has fallen to 50,000--compared with about 1.6 million ethnic Albanians. In Pristina, a prewar Serbian population of 40,000 has fallen to just 1,000.

Against that background, Albright basked in the cheers of several thousand ethnic Albanians in central Pristina and promised they will no longer have to fear oppression from Belgrade--capital of both Yugoslavia and its dominant republic, Serbia--but she also told the crowd that their freedom must be "based on tolerance, law and respect for human rights."

"Never again will people with guns come in the night," she said. "Never again will houses and villages be burned, and never again will there be massacres and mass graves."

In a private meeting earlier with Hashim Thaqi, the KLA political leader, Albright said that the group must recognize that the United Nations will be the ultimate authority here for the immediate future, a senior U.S. official said. The official did not characterize Thaqi's response.

The agreement ending NATO's 11-week bombing campaign against Yugoslavia provided for continued Serbian sovereignty over Kosovo--at least in theory--but stipulated that the United Nations would be the governing authority pending provincial elections, and that a NATO-led peacekeeping force would serve as the guarantor of security for ethnic Albanians and Serbs alike.

As Thaqi arrived for the meeting at the U.N. mission here, a shot rang out, leading some U.S. officials to reconsider whether Albright should address the crowd as scheduled. The source of the gunfire was never determined, but Albright insisted on speaking, officials said.

Later, Albright traveled to a monastery outside Pristina to meet Serbian Orthodox Bishop Artemije, to whom she stressed that NATO and the United Nations are committed to a multiethnic Kosovo and want Serbs to continue to live here. Several hundred Serbs demonstrated outside the monastery, shouting "Serbia!" and "Slobo!"--a reference to Yugoslav President Slobodan Milosevic.

According to a U.S. official, the bishop told Albright that the demonstrators were for the most part not Kosovo Serbs, but had been bused in from Belgrade. The Serbian Orthodox Church has called on Milosevic to resign, and church leaders have acknowledged that ethnic Albanians were the victims of major crimes by Serb-led Yugoslav troops and Serbian police forces during the Belgrade government's brutal spring campaign to purge the province of its ethnic Albanian majority.

Albright described the killing of the Serbian farmers as "dreadful," but she also pointed out that some "pretty disgusting things" had happened to the province's ethnic Albanians in the past few months--a conjunction of atrocities that some Serbian leaders found less than sympathetic to their recent grief.

Zoran Andjelkovic, the Belgrade-appointed Kosovo governor who has been ignored by foreign officials here since the arrival of the NATO-led peacekeepers, said her remarks showed a lack of humanity. In response, a U.S. official declared: "Some Serbs need to face the fact that they are in a deep, deep hole that they dug themselves."

Andjelkovic said in an interview that the Kosovo Serbs are willing to cooperate with NATO and the United Nations, but he complained that the United Nations seems willing to deal only with those Serbs--such as church leaders--who condemn Milosevic. Andjelkovic, for instance, has not been invited to U.N.-sponsored meetings of Serbian and ethnic Albanian leaders.

After leaving Kosovo this evening, Albright met in Rome with Ibrahim Rugova, leader of the ethnic Albanian Democratic League of Kosovo, a political rival of the KLA. Albright's spokesman, James P. Rubin, told reporters afterward that Rugova promised to return to Kosovo immediately.

Rugova has infuriated Western officials by not remaining in Kosovo since the war ended, facilitating the KLA's emergence as the dominant force there. Rugova also has refused to participate in an interim government, headed by Thaqi, that was set up by agreement between his party and the KLA during failed peace talks in France before the war began.

Albright plans next to attend Friday's Balkan stability conference in Sarajevo, which President Clinton and 40 other world leaders will attend. In proceedings there today, Finnish President Martti Ahtisaari warned Balkan leaders that they must bury their conflicts if they want European and U.S. reconstruction aid or hope to enter the European Union.