With ethnic Albanian guerrillas establishing offices, erecting checkpoints and occupying police stations in Kosovo as Yugoslav forces have withdrawn, NATO commanders moved for the first time today to rein in the newly empowered rebels and allay concerns among Serbian civilians here about possible reprisal attacks.

In the first major confrontation between Kosovo Liberation Army rebels and allied forces, U.S. Marines today stripped weapons from about 200 guerrillas in the Kosovo village of Zegra. The action followed a tense standoff in which the KLA members refused at first to surrender their weapons, then complied when the Marines used armored personnel carriers and Cobra helicopter gunships to intimidate them. The Marines then led away six rebel leaders in handcuffs.

With the last Yugoslav army and Serbian police units withdrawing from southern Kosovo, the flow of refugees returning to the shattered Serbian province picked up speed despite appeals from NATO and aid officials concerned about lack of food for them and the dangers of land mines. More than 11,000 ethnic Albanian refugees crossed into Kosovo through the Morina border station in Albania during the day, creating a three-mile-long traffic jam from refugee camps in Kukes, 10 miles away.

"Unfortunately, it's an avalanche," said Rupert Colville, a spokesman for the U.N. High Commissioner for Refugees.

In Helsinki, U.S. Defense Secretary William Cohen said the status of 200 Russian troops who have been occupying the airport here in the Kosovo capital since Saturday may be resolved on Thursday, following what he described as productive talks there today with his Russian counterpart on Russia's role in the international peacekeeping force.

As the deployment of NATO troops into Kosovo proceeded through a fifth day, Kosovo Liberation Army forces continued to take up positions in towns and cities on the heels of departing Serb-led Yugoslav forces, which are withdrawing under terms of last week's NATO-Yugoslav military agreement.

The increasingly visible KLA presence has alarmed the Yugoslav military and Serbian civilians -- thousands of whom are fleeing Kosovo into Serbia proper out of concern the rebels may seek to take revenge for atrocities against Kosovo's ethnic Albanian majority. At the Pentagon, a Defense Department spokesman told reporters today that NATO troops had come upon or were told about 90 suspected mass-grave sites since entering Kosovo on Saturday.

The emboldened KLA -- numbering about 10,000 -- has also raised concerns within NATO, which is committed to the demilitarization of the rebel force under a U.N. Security Council resolution that authorized deployment of the Kosovo peacekeeping force.

"I'm well aware of your concern over the KLA," British Lt. Gen. Mike Jackson, commander of the peacekeeping force, told about 300 Serbs today in a Pristina neighborhood from which Serbian civilians have been leaving in droves over the past two days as the rebels move into the city. "The U.N. Security Council resolution makes it absolutely clear this organization is to be demilitarized."

Jackson said he expects NATO and KLA leaders to sign an agreement within the next two to three days that would demilitarize the guerrilla force over the next month. He said there would be a "strict program" under which the rebels would turn over their weapons.

"My force does not tolerate threatening behavior, wherever it comes from," Jackson told the Serbs, many of whom rolled their eyes in skepticism at his words. "I ask you to stay in your homes here in Kosovo. The world has too many refugees already. I beg you not to make the numbers greater. Stay at home!"

A KLA leader told reporters that his group is prepared to surrender its heavy weapons but would not easily part with small arms, such as rifles, which he said they are not mandated to give up under the Security Council guidelines. "Heavy weapons will be turned in on a voluntary basis," KLA spokesman Dino Asanaj said. "The . . . [KLA] will not be an obstacle to peace."

Demilitarizing means, in part, that the KLA would be required to turn in a certain number of weapons that NATO would then destroy. NATO officers negotiating the plan with the KLA said that once the two sides have reached agreement on the demilitarization plan it will be presented to NATO political authorities for approval.

At the border crossing at Blace, Macedonia -- where tens of thousands of refugees arrived within days after the Belgrade government launched a campaign to purge Kosovo's ethnic Albanian majority in late March -- the number of refugees returning to Kosovo has doubled each day this week, with an estimated 1,500 walking and driving across the border by noon today.

On the road north from the border, cars and tractor carts carrying returning refugees intermingled with convoys of fleeing Serbian civilians, a scene that underscored the predicament of NATO commanders who now find themselves pleading with one population not to return home and begging another not to leave.

The ethnic Albanians' joyous and triumphant return to Kosovo today contrasted sharply with their grim arrival in Macedonia and Albania over the last 2 1/2 months as dejected, traumatized refugees fleeing a brutal forced deportation campaign. At the Albanian border, each vehicle entering Kosovo received a handout on the dangers of land mines, booby traps and unexploded bombs. But many refugees said the fear of what they would find was overcome by the prospect of returning home.

While the refugees were urged to be wary of land mines, it was unclear when troops would de-mine remote villages and check private homes for booby traps. German NATO officials in Prizren, a southern Kosovo city 12 miles from the Macedonian border, said they were de-mining only for their own operational purposes.

"We think there might be mines," said Nait Memaj, whose tractor was towing a wagon loaded with 23 family members home to Zhur, a border town where three people were recently injured in a mine explosion. He simply shrugged. "We're going home anyway."

Relief officials said the sudden rush of returning exiles and the resultant traffic jams were creating severe logistical problems for aid groups moving food into Kosovo. The German officials said they plan a helicopter food delivery Thursday to the town of Musutiste, about 12 miles northeast of Morina, as part of a new emphasis on helping returning refugees.

Stephen Green, head of operations for the U.N. World Food Program in Kukes, said the organization is negotiating with the KLA to distribute food in rural areas. "Prizren is accessible, but the need is in the communities outside it," he said.

The U.N. food agency was distributing flour, oil and rice at six places in Prizren today, and aid workers stood at the edge of town tonight handing out loaves of bread to arriving refugees.

In Albania, the agency is assembling food packages containing 37 pounds of supplies for each returning refugee. It also was preparing for refugees who might come to Kukes for several days while waiting for family members to cross the border and report back on conditions, Green said. "We're close to being overwhelmed here," he said.

No representatives of the U.N. refugee agency were present at the Blace, Macedonia, border crossing today despite a sign announcing their presence at a dilapidated former duty-free shop. KLA rebels and U.S. Army troops offered first aid, water and greetings to the returning refugees.

Ragip Beqa, 53, arrived with a bleeding lip and a hand that had been split open, he said, by a Macedonian border guard who hit him with a hard object after he asked the guard if he could take his ailing wife to the front of the long line of people waiting to cross. U.S. soldiers said they have administered first aid to several refugees who have been roughed up by the Macedonian guards.

After a soldier patched up Beqa and advised him to "see a doctor and get some stitches," Beqa began the 15-mile walk to his mountain village, where he said his house had been burned and allied forces had marked the narrow dirt road with mine warnings.

"I will be the mine tester," said Beqa, wiping his lip. "If somebody has to die, it will be me and not my children."

Pulling a small metal cart containing the plastic sheeting he had purchased to build a tent for his extended family, Beqa and his panting wife trudged up the twisting dirt road between strips of white tape -- the boundary of mine fields marked by NATO troops.

"Tell them we've only cleared the mines about 10 yards down the road," cautioned a British soldier who was unable to dissuade the determined couple from heading home. "There's no guarantee what they will find."

Moore reported from Pristina and General Jankovic, Yugoslavia, and Anderson from Morina, Albania, and Prizren, Yugoslavia.

CAPTION: Yahir Ahmeti, an ethnic Albanian who had been hiding from Serbian police in Kosovo, greets his children at the Kosovo-Macedonia border, where they and thousands of other refugees have been lining up to go back home.


U.S. Army Pfc. Carl Adams bandages the hand of Kosovo refugee Ragip Beqa, who said he was struck in the face and hand by a Macedonian border guard.