BELGRADE, Yugoslavia (AP) _ Making good on months of threats, NATO launched airstrikes on Kosovo tonight to punish Yugoslavia and its hard-line leader for refusing to make peace in the southern Serbian province.

Detonations went off in Pristina, lighting the hills over the darkened Kosovo capital.

In Belgrade, witnesses reported eight explosions, some near the Batajnica military airport and at least one near a power plant.

Belgrade TV reported that one NATO plane was shot down in the Cicavica Mountains, northwest of Kosovo's capital Pristina, according to Yugoslav military forces. NATO officials in Brussels, Belgium, said they were aware of the report, but they could not immediately confirm it or deny it.

In neighboring Montenegro, which with Serbia forms Yugoslavia, an army military barracks in Danilovgrad was in flames after being hit. Three soldiers were reported wounded and taken to a hospital.

Explosions also were heard in the area of Novi Sad in northern Serbia, northwest of Belgrade.

The Yugoslav army declared a state of war shortly after the first wave of attacks said more than 20 targets were hit in the first hour of the assault. It said no air defense units were damaged.

State radio had no report of the airstrikes for the first few minutes, playing Serbian music instead. Electricity soon went out in Pristina, leaving the city of a quarter-million people in the dark, lighted only by the glow of distant explosions.

U.S. B-52 bombers had taken off from their base in Britain more than seven hours before the attack, after NATO gave the go-ahead for allied airstrikes on Yugoslavia.

Waves of jet fighters, perhaps 70 from the NATO alliance including 10 stealth bombers, also headed across the Adriatic Sea from the Aviano air base in northern Italy.

Dozens of cruise missiles and one-ton bombs were fired at Yugoslav targets in a bombardment that also involved the B-2 stealth bomber, used in combat for the first time.

The attack, announced by NATO Secretary-General Javier Solana at alliance headquarters in Brussels, Belgium, and confirmed minutes later by President Clinton in Washington, was the first against a sovereign country in NATO's 50-year history.

``Kosovo's crisis is now full-blown and if we do not act clearly it will get even worse,'' Clinton said.

Detonations were first heard in Pristina about 8 p.m. (2 p.m. EST), signaling the start of the NATO bombing campaign.

Details on the effects of the airstrikes were sketchy at first, with the targets spread over a broad area of Yugoslavia. NATO gave no account of the assault.

Threatened for months, the punitive strikes come as a result of Yugoslav President Slobodan Milosevic's repeated refusal to end the war against ethnic Albanian separatists and accept a Kosovo peace plan.

``We must now act,'' British Prime Minister Tony Blair said earlier today, declaring the world must end a year-old war that has killed more than 2,000 people and driven some 400,000 from their homes.

Two days of last-ditch talks between special U.S. envoy Richard Holbrooke, who brokered an end to the Bosnian war in 1995, and the Yugoslav leader failed to change Milosevic's mind.

Before the attack, Milosevic delivered a final message of defiance, urging Yugoslavs in a televised address to defend the country ``by all means.''

``What is at stake here is the freedom of the entire country,'' Milosevic said, reiterating his refusal to accept the U.S.-backed plan and its call for 28,000 NATO troops _ including 4,000 Americans _ to enforce peace in the province.

Fighting raged in several Kosovo villages today.

Serb tanks fired volley after volley into areas near Kosovo's southern border with Macedonia, and Associated Press Television News journalists saw about 100 houses ablaze in three devastated villages close to the border.

An estimated 40,000 Yugoslav army and Serbian police forces are in Kosovo, pursuing the crackdown Milosevic launched in February 1998 to try to crush ethnic Albanian rebels in the poor southern province of Serbia, the dominant republic in Yugoslavia.

NATO had threatened bombardment if Milosevic rejected a U.S.-brokered plan to provide interim self-rule to the ethnic Albanians who make up 90 percent of Kosovo's 2 million people.

The NATO onslaught, which officials said could last for days, was to rely initially on cruise missiles launched from allied warships in the alliance's Mediterranean fleet.

Western allies said the door was open at any time for Milosevic to accept the Kosovo deal.

``One phone call from Milosevic would be enough. That is possible at any time and the whole military process will be stopped,'' German Foreign Minister Joschka Fisher said at a European Union summit in Berlin.

More than 400 warplanes were poised to attack from NATO bases in Italy, and the NATO Mediterranean fleet, which includes eight warships from eight countries, sailed from Trieste.

Eight U.S. B-52 bombers, each armed with 20 cruise missiles, were the first to depart for action for NATO today, flying from their base in England.

``We must stop the violence and bring an end to the humanitarian catastrophe now taking place in Kosovo,'' Solana said in announcing the airstrikes. ``We have a moral duty to do so.''

Ahead of the attacks, Yugoslavia declared a state of emergency Tuesday _ its first since World War II _ and ordered its forces dispersed to hide from bombings and try to keep the country's grip on Kosovo, which Serbia considers the historical cradle of its culture.

Long lines at gas stations and unusually deserted streets told a stark story in Belgrade, where many people went on last-minute panic shopping sprees.

The first NATO attacks were expected to target the tough Yugoslav air defense system, which has numerous surface-to-air missiles that could down allied aircraft.

Four years ago, during NATO strikes against Serbs in Bosnia, an American F-16 was shot down by a surface-to-air missile.

Russian President Boris Yeltsin today made a final appeal today to Clinton, urging the president in a half-hour phone call not to take the ``tragic step'' of bombing Yugoslavia.

China also opposes airstrikes, saying the Kosovo crisis is an internal affair, and fellow Slavic nations Belarus and Ukraine voiced support too today for Yugoslavia.

``The fire in Kosovo could engulf the whole Balkans,'' said Turkish Prime Minister Bulent Ecevit.

In New York, the U.N. Security Council, acting on a Russian request, met in emergency session and Secretary-General Kofi Annan chided the Western alliance for failing to involve the council in its decision to use force.

``The council should be involved in any decision to resort to the use of force,'' Annan said.