The three heavily armed policemen came knocking at 8:15 a.m. a few weeks ago at a house on Gavran Street in the center of the Kosovo city of Gnjilane.

They sat down at the kitchen table with green forms in hand and demanded that Isuf, the 38-year-old homeowner, help them create a detailed record of the ages and birthplaces of everyone who lived there.

After 45 minutes of questioning, they gave Isuf and the other seven members of his family special residency cards with an official stamp in the corner. They said that without these cards, the family was not entitled to stay in Gnjilane. They warned that anyone who was not registered could be killed. Then they moved on to the house next door.

Similar scenes have unfolded recently in cities throughout Kosovo as Yugoslavia's policy of "ethnic cleansing" -- expelling or killing hundreds of thousands of ethnic Albanians -- moves into a new phase. In the view of Western human rights experts here and in Albania, it is no less ominous than earlier phases.

After being pursued for two months by forces employed by the army and the Interior Ministry, the government's program has been turned over to bureaucrats. They are now creating a detailed accounting of who lives in Kosovo -- the first since 1981 -- thereby trying to streamline and simplify the task of deciding who can stay and who must leave.

The patterns of the new displacement are already evident: Only those who still have identification cards and other documents issued before March 20 can obtain new residency cards. This leaves out hundreds of thousands of people whose identity papers were destroyed by police or left behind when they were forced to flee their homes. None of these people will be able to return if the government's new policy sticks.

In addition, police are requiring that the new cards be obtained in the towns where residents lived before March 20. Since many of these towns were burned to the ground by government forces or lie behind the battle lines that still exist between Yugoslav troops and separatist rebels, this rule excludes hundreds of thousands of additional ethnic Albanians from meeting the new residency requirements.

Those who were expelled from their villages in Kosovo and fled into the mountains before migrating back to major cities in search of food are not entitled to stay in these cities, police have told them.

And if they must move from the cities, the only path open to most of them is to head for neighboring Albania or Macedonia, according to dozens of refugees interviewed after their arrival at camps here.

Coupled with recent claims by top Yugoslav officials that Kosovo never had more than 800,000 ethnic Albanians -- roughly a million fewer than Western governments said were there before hostilities broke out last year -- the new registration cards create a pretext for the government to bar reentry, Western officials say. Kosovo is a province of Serbia, Yugoslavia's dominant republic.

"It's a way to complicate" the return of ethnic Albanians to their previous homes, said Sandra Mitchell, human rights director at the Kosovo Verification Mission of the Organization for Security and Cooperation in Europe (OSCE). "It could complicate citizenship and identification. It could contaminate and pollute any kind of existing property records or election database that exists. . . . It's a pattern that we've seen in other conflicts that Milosevic was involved in."

Although the registration effort has been underway for weeks, the details have emerged only in the past few days from refugees trickling across the Macedonian and Albanian borders.

As a result, monitors still do not know how many people are affected by the change. Qamile Sadiku, 34, said, for example, that the police came to his home in Urosevac two weeks ago to tell him that he must register the eight members of his family "or leave. . . . We didn't have any choice."

Many refugees interviewed here and in Albania say they fled rather than try to obtain the cards, because they feared the prospect of a face-to-face meeting with Serbian officials. Although fighting between rebels and troops has diminished in many cities, such meetings can get out of hand, according to refugees.

After hiding in basements for weeks, "a lot of men went to get this document and were sent to the prison" after being stopped by police on the street, said Isuf as he stood in line to register for a food card at the Brazda refugee camp.

He said he had obtained the identity card but fled with his family anyway, because "we were afraid that once they knew everything about us, they could just take people to the prison -- fighting-age men."

Alistair Brown, a human rights monitor for OSCE, confirmed that "some people are leaving because they do not want to register their details. "That itself is a form of coercion to start pushing people out . . . without going to one of the extreme measures."

For example, Hyra Haxholli, 43, who lived on Proleter Street on the north side of the Kosovo capital of Pristina before fleeing to Macedonia, said she had decided not to get the registration card "because of my sons," aged 15 and 17. "Then they made me leave because we didn't have the card. They said that if we don't have all the people who are here registered, we will kill you. The policeman knew us, and he said that if he ever saw anyone running away [in an effort to elude detection], he will shoot."

Many refugees have said that the demands for registration cards came after police had already made several visits to their homes -- first to see who was there, and then to write down the names of any relatives or refugees.

The card lists a resident's name, birth date, birthplace, address and neighborhood. Every member of a family -- even babies less than a year old -- must have one.

In Pristina, residents were ordered to pick up the card at a bank on the city's main street, where police moved after NATO warplanes bombed their headquarters. Outside the entrance is a policeman who admits only those who still have documents proving their residency in Pristina before the war, said Selami Gashi, 34.

He was unable to get one, and fled in fear. "They are cleansing Pristina," he explained.