Nasir Hajdari was summoned to the door of his third-floor apartment late last month here in the town where President Clinton today hailed the progress Kosovo has made toward a return to normal life. Outside were three men who identified themselves as employees of the provisional Kosovo government run by Hashim Thaqi, political leader of the now-disbanded Kosovo Liberation Army.

The three had a message for the ethnic Albanian family: Hajdari and his wife and three children were no longer entitled to live in that flat; they had to vacate the premises to make room for new occupants selected by Thaqi's rebel-led government.

In recent days, the message has been heard with growing frequency by Kosovo's Albanians as well as its Serbs. Despite the U.N. administration here, Thaqi's government of former soldiers has declared itself the sole arbiter of which citizens have a right to preferred accommodations in the freezing temperatures that have descended on this Serbian province.

Such actions are illegal, according to U.N. officials charged with administering Kosovo's recovery and implanting a democratic system under the protection of a 40,000-member international peacekeeping force. Lt. Col. Michael Ellerbe, commander of U.S. peacekeeping forces in Urosevac, said his troops arrest people carrying out such evictions with growing frequency.

Despite the arrests--and the lack of any effort by rebel leaders to hide their actions--top U.N. officials say the evictions have largely occurred without their knowledge. But the evictions are part of what U.N. police officers and NATO officials in four of Kosovo's major urban centers describe as growing evidence of government-organized illegal activities by former rebel fighters in Kosovo.

Former KLA guerrillas were among the ethnic Albanians who moved quickly after the war ended in June to push out Kosovo Serbs and take their property. The difference now, the officials say, is that former KLA fighters have been organized into groups that intimidate Serbs and ethnic Albanians alike to appropriate apartments, collect fees or gain access to rent money from the flats.

The KLA officially ceased to exist two months ago, under an agreement its leaders reached with NATO. But some of its leaders, including Thaqi, run an unofficial ethnic Albanian government that operates alongside the United Nations and openly prepares for the day when Kosovo is independent in law as well as in fact. Meanwhile, more than 10,000 former KLA members have been issued new identity cards signifying their application for 5,000 slots in a successor organization approved by NATO and called the Kosovo Protection Corps.

U.N. police and NATO soldiers have seized hundreds of identity cards from former KLA troopers at crime scenes in the past four months, said a U.N. police official. Although some cards have been found to be forged, another U.N. official following the rise of crime said most of his colleagues believe the former rebels "are systematically threatening people, evicting people . . . [and] trying to collect illegal taxes."

For example, the 1,300 or so trucks passing the Macedonian border every day for months have been routinely forced to pay a customs duty of $20 apiece to agents of the Thaqi government, despite claims by the U.N. administration that it must be the sole recipient of public revenues in Kosovo, according to police and former KLA officials.

Thaqi's aides deny that any such taxes still are being collected by his government. But documents recently seized in Urosevac show a businessman was ordered to pay $400 in taxes two weeks ago and that the government has established an elaborate sliding scale of illegal taxes for cigarettes, alcohol, juices, coffee and gasoline.

Some Western officials say such fees sometimes may be collected with an implicit threat of force. In the Serb enclave of Globocica, for example, a Muslim Slav complained to Western human rights monitors early this month that his shop was blown up after he refused to pay a registration fee to the government. No conclusions were reached in that case.

But Western officials say they have confirmed complaints from ethnic Albanians, Roma and Serbs in the cities of Prizren, Pristina and Djakovica that they have been threatened with violence or even kidnapped to force their withdrawals from apartments by men who identified themselves as police in Thaqi's Ministry of Public Order, according to police reports.

Rexhep Selimi, 28, a former soldier whom Thaqi appointed to head the ministry in July, acknowledges that some evictions have occurred but denies they are unfair. He said in an interview that he knows the group's actions are not legal, but says they are nonetheless "morally" justified by the urgent need to allocate scarce housing to the most worthy citizens, including people living in tents, former KLA fighters and their families.

Selimi said the Public Order ministry has 1,500 members--who receive average salaries of $225 a month--whom he hopes will form the nucleus of a new ethnic Albanian police force under U.N. supervision.

He said the ethnic Albanian government has stepped into a vacuum left by the United Nations, which he said is administering the province "like this is just a movie, more like acting than real work." He acknowledged that if occupants of a targeted flat refuse a "suggestion" to leave, then "we escort them out." If they resist, he said, "we are the ex-KLA and we know how to deal with these cases."

Selimi and other former KLA fighters say they consider it reasonable to give housing priority to the families of soldiers or to needy former KLA fighters--particularly since some ethnic Albanian civilians unjustifiably seized more than one flat during a massive postwar scramble for living space. To accomplish their work, he said, the ministry's police are amassing a comprehensive apartment-by-apartment tally of who lives where, where they are from, whether they own their flat and whether they have KLA permission to stay.

Selimi said the housing reallocations have been finished at the village level and now focus on urban centers. Ministry documents indicate that 64 apartments were handed out in Urosevac during a 15-day period ending Oct. 1.

Although the work is ostensibly overseen by special municipal commissions, these are controlled by ex-KLA officials under the supervision of Thaqi, who is aware of the eviction effort, several officials said.

NATO troops seized one eviction notice, for example, that ordered a flat in Urosevac be given to someone wounded in the war; it was signed by Shukri Buja, a former KLA regional commander slated for a top job in the Kosovo Protection Corps.

But Dennis McNamara, the U.N. official responsible for humanitarian issues, said only U.N. administrators have "the authority to make those adjudications." He added that a list of priorities including former KLA fighters is "not a list I would be part of," because the United Nations' aim is to find homes for the "most vulnerable"--those who cannot rebuild their homes, households headed by women, the elderly and the sick.

Ellerbe and other U.S. troops say their aim is to block actions by organizations attempting to usurp U.N. authority and to enforce a form of "squatters rights" through the winter until a U.N. commission on property ownership can begin to function. The commission was formed a few days ago.

In the Hajdari case, the family says it took over the flat after their house was burned in the war. After they complained, U.S. soldiers arrested three men at the Public Order Ministry on charges of illegal intimidation and put them in the brig at nearby Camp Bondsteel. But top officials at the camp later asked that no more such suspects be sent there.

A spokesman for General Agim Ceku, new commander of the Kosovo Protection Corps, said "the real members" of that group had no role in evictions or any criminal activities. "For the KPC, the life and the property of every citizen of Kosovo is sacred, and it is our firm conviction that whoever acts against the life and the property of the other should be treated as a criminal," the group said in a statement several weeks ago.

CAPTION: President Clinton greets U.S. troops at Camp Bondsteel near Urosevac. Clinton told U.S. peacekeeping soldiers that their example can help overcome the sectarian violence that still grips the Serbian province of Kosovo.

CAPTION: An ethnic Albanian boy listens intently to President Clinton during a brief stop in Urosevac in Kosovo.