KOSOVO REFUGEE FLOOD ON WAY; 100,000 MORE FLEE TOWARD MACEDONIA.

Byline: John Donnelly and Barry Shlachter Knight Ridder Newspapers

While NATO officials announced ``one of the best nights'' yet in their 3-week-old air war against Serb troops, the news from Kosovo got worse Friday, with reports that as many as 100,000 more ethnic Albanian refugees are heading toward fragile Macedonia and U.S. spy satellites have photographed what appear to be mass graves.

Late Friday, the Defense Department announced that a Yugoslav officer had been captured in an operation Tuesday night by ethnic Albanian insurgents inside Kosovo. They turned over the unidentified officer to Albanian authorities, who delivered him to U.S. military custody. He was flown to Tirana, the Albanian capital, on a U.S. military helicopter Friday.

The Pentagon said the Yugoslav officer, who was found by a doctor to be in good health, is being treated as a prisoner of war and will be visited by a representative of the International Committee of the Red Cross. Serbian officials have not permitted the Red Cross to visit the three American servicemen who are being held in Yugoslavia.

Meanwhile, in Brussels, NATO spokesmen said the alliance's attacks Thursday night damaged surface-to-air missile sites, radars, control vehicles, tanks and artillery, MiG-21 warplanes at the Pristina airfield in Kosovo and an ammunition depot in the Kosovo provincial capital. NATO warplanes also hit an airfield in the Yugoslav republic of Montenegro.

Yugoslav authorities claimed 20 civilians were killed in the latest wave of attacks, and declared Friday a day of mourning for what Belgrade called ``NATO's atrocities'' against a refugee convoy in southern Kosovo. Serb officials said the attack Wednesday killed 75 people and wounded dozens.

Claims hard to confirm

In all, Yugoslavia claims that NATO's air war has killed 500 civilians and wounded more than 4,000 people, but those figures cannot be independently confirmed. Serb authorities have expelled a number of Western reporters and severely limited the movements of the few Western journalists who remain in the country.

But reports from refugees and other sources Friday clearly showed an escalating Serb campaign to push ethnic Albanians out of Kosovo and into neighboring Macedonia, Albania and Montenegro. Western officials said it appeared that Yugoslav President Slobodan Milosevic is attempting to destabilize Macedonia, the poorest country in Europe, and also the pro-Western government of Montenegro.

NATO satellite photographs and pictures from unmanned airplanes have shown ``large trails of people moving to the Macedonian border again'' since Wednesday afternoon, said a Clinton administration official, speaking on the condition of anonymity. Columns of people also are headed toward Montenegro and Albania.

Ron Redmont, a United Nations relief agency spokesman, estimated that 100,000 new refugees were headed for Macedonia, including 50,000 from the Gnjilane area of southern Kosovo and another 20,000 from the town of Urosevac. By noon Friday, 6,000 new refugees had arrived in the last 24 hours, pushing Macedonia's refugee population to more than 122,000.

Macedonia issues warning

``The expulsions which were put on hold or slowed down over the last two weeks have now resumed with full force,'' Kris Janowski, also a U.N. spokesman, told reporters. ``The effort by the Serb authorities to expel the entire ethnic population of Kosovo is again under way.''

Macedonia, which says it is hosting five times more refugees than it can handle, warned Friday that other countries must share the burden. Another problem, said Interior Minister Pavle Trajanov, was that the Kosovo Liberation Army appeared to be using Macedonia as a base to launch attacks against Serb troops.

``We sincerely hope that the hospitality of Macedonia and its people will not be abused in any way,'' Trajanov told reporters in a room full of weapons, ranging from Kalashnikov rifles to anti-tank weapons, confiscated from KLA guerrillas.

The president of the Yugoslav republic of Montenegro, Milo Djukanovic, warned that the conflict could sweep through the rest of the Balkans. Djukanovic also told the Yugoslav army to stop interfering in his republic's internal politics.

Meanwhile in Washington, Rubin said NATO had new evidence of mass graves southwest of Pristina in Kosovo.

``We're not talking about a few dozen. We're talking about more than that,'' Rubin said.

But an administration official who asked to remain anonymous cautioned that satellite imagery was still being studied. ``They have got evidence of what they believe are fresh diggings,'' the official said. ``Whether they're graves or not, we don't know for sure yet.''

President Clinton, addressing an audience in Detroit, pressed his case for why it is important for NATO to intervene in Kosovo. One of the most compelling arguments for intervention, he said, is to think about the cost of not getting involved.

``How would you feel if I'd come here to give this speech today and the headlines were full of all those people being killed and all those people being thrown out of the country and we were having to explain to people why we couldn't lift a finger to do anything about it?'' he said.