Heavily armed guerrillas, some of them wearing explosive belts, stormed into a school in southern Russia near the separatist region of Chechnya on Wednesday morning and took several hundred students, teachers and parents hostage after a deadly shootout.

Striking right after opening-day ceremonies for the new academic year, the attackers threatened to blow up the school if the Russian government attempted to retake it and said they would execute 50 hostages for every one of their own killed.

As many as seven adults died in an initial shootout at School No. 1 in the North Ossetian town of Beslan, just west of the Chechen border, authorities said. Gunfire and explosions rang out in the area throughout the day and into the night, after Russian troops surrounded the school.

The raid came as Russians were still absorbing the carnage of three other bombings elsewhere in the country during the past week -- the downing of two airliners and a suicide attack in Moscow that together killed about 100 people. Russian authorities have blamed Chechen separatists for those attacks.

Nearly 24 hours into the siege in Beslan, anxious parents continued to hold vigil at the local House of Culture. The auditorium there was a study in a state of grief, with deadened, drawn faces of women who had cried themselves out and men bristling with barely suppressed anger. Some families had four or five children at the school; an 11-month-old was also on the list circulating among the parents. As many as 885 children are registered at the school, which comprises Grades 1 through 11.

Just before news of the school seizure broke, President Vladimir Putin said Chechen terrorists linked to al Qaeda were responsible for the recent outbreak of violence and vowed not to negotiate with them. "We shall fight against them, throw them in prisons and destroy them," he said before flying back to Moscow from vacation on the Black Sea for the second time in a week.

"War has been declared on us," added Putin's defense minister, Sergei Ivanov, "where the enemy is unseen and there is no front."

At Russia's request, the U.N. Security Council called an emergency meeting Wednesday in New York to discuss the latest spasm of Chechen-related terrorism. At the meeting, the council condemned "in the strongest terms" the attack on the school and demanded "the immediate and unconditional release of all hostages." President Bush phoned Putin to offer support and told him the United States was fighting "side by side" with Russia in the war on terror, Bush spokesman Scott McClellan told reporters.

By nightfall, the town of Beslan, with a population of 30,000, had settled into a tense standoff, with the school surrounded by hundreds of Russian troops, armored vehicles and parents desperate for information about their children trapped inside. But there was no encouraging news for them, just a police officer who told the frantic relatives via bullhorn about the hostage takers' demands.

"The only thing they said was that they would kill 50 hostages for each one of them killed, 20 for each wounded. If the storming begins, the whole school would be blown up. That's all we can say for the moment," the officer said on the bullhorn in a scene later broadcast on television across Russia.

The attack began about 9 a.m. when a large group of guerrillas rolled up in a military-style truck and charged into the school as the opening-day ceremony was ending in the gym. At least two of the attackers were women wearing explosive belts. Some local police immediately resisted the intruders, exchanging fire with them.

Taimuraz Pukhayev, who lives across from the school, saw the attack start. His wife had just taken his three children -- ages 7, 11, and 12 -- to class when he heard shooting. He ran outside and saw about half a dozen camouflage-clad guerrillas and two women rushing toward the building. "I saw them breaking the doors, the windows. I heard children screaming," he said. Then a guerrilla with an automatic rifle started shooting at him. "They shot at me, then they noticed [a neighbor] and shot at him. I saw him bleeding from the head." The neighbor later died.

Some children ran to safety in the initial confusion. "I thought it was a joke, but they began to shoot in the air and we ran," said one breathless boy shown on Russia's NTV television network.

For Elza Baskayeva, editor of the local newspaper, a fearful wait began when she heard shooting and called her 27-year-old daughter, who was at the school taking pictures for the paper. "She was crying, 'They are shooting! They are shooting! We are on the second floor.' And then I lost the connection," Baskayeva said in a telephone interview. Baskayeva went to her office a few hundred yards away and learned that two other employees and their children had also been taken hostage.

Soldiers surrounded the school within an hour, she said.

By midafternoon, about 15 children whose teacher had hidden them in the boiler room had run to safety, Baskayeva said, but there was no word on the others.

At the House of Culture, "the parents were very mad. They are saying that the militia is not protecting us all," she said.

"No one gives us real information, that's the most terrible thing," said Madina Gulyarova, 39, who had a 10-year-old nephew in the school. "We see on TV that the whole world supports us. But nobody from our authorities will speak to us."

Svetlana Kaitova barely held back tears as she talked about her 22-year-old daughter, who had started her teaching job that morning. "When I woke up this morning, I was such a happy mother. I gave education to my children, they were all working, and now look what's happened," she said.

Lev Dzugaev, spokesman for the emergency headquarters, said authorities had managed to establish phone contact with the hostage takers only Wednesday evening. "We hope we will be able to conduct negotiations and we will learn what they really want," he said by telephone from Beslan. At least initially, he said, they did not make specific demands.

But Putin's top aide for Chechnya, Aslanbek Aslakhanov, told Russian reporters that they demanded an immediate Russian withdrawal from Chechnya and the release of guerrillas captured during a raid this summer in the neighboring region of Ingushetia. He said they asked to negotiate directly with the presidents of Ingushetia and North Ossetia, as well as a children's physician, Leonid Roshal, who acted as a mediator during the 2002 siege of a Moscow theater by Chechen rebels.

When the president of Ingushetia did not show up, the hostage takers refused to see Roshal, though he was in telephone contact with them, officials said.

Early Thursday morning, as a heavy mist settled around the school, Lt. Gen. Kazbek Dzantiyev was confronted by angry parents he tried to placate by saying, "We're not going to hide anything from you." The head of the local interior ministry, Dzantiyev said there were 400 children and an unknown number of adults taken hostage by as many as 40 terrorists. A local police officer was under investigation, he said, for helping the hostage takers, who included Chechens, Russians, Ingush and Ossetians.

But official figures varied for how many people had been taken hostage; Dzugaev said it was 354, of whom approximately half were children. He said four to seven civilians were confirmed dead in the initial seizure. Russian news agencies said as many as 11 died.

Officials said the hostage takers were refusing to allow any food or drink for the children.

To many Russians, the day's events were a shocking echo of similar seizures by Chechen rebels that resulted in mass civilian casualties.

In 1995, during the first post-Soviet war in Chechnya, more than 100 civilians died as rebels seized a hospital in the town of Budennovsk. After five days, President Boris Yeltsin allowed the guerrillas to leave in exchange for freeing their captives.

Two years ago, Putin took a different tack when Chechen rebels took over a Moscow theater during the popular musical "Nord-Ost." After a 57-hour standoff, Putin ordered the theater stormed, and 129 hostages died as a result of the knockout gas used by authorities.

"Unfortunately, there are only two scenarios in Russia," said Aleksandr Golts, a military expert. "The first is Budennovsk: give permission to the terrorists to go where they want and accept this shame. That's how Yeltsin behaved. The other variant is 'Nord-Ost' -- poison gas, storm and everything. That's how Putin behaves."

Glasser reported from Moscow.

An image taken from TV shows a soldier rushing a girl away from the school in Beslan, in the region of North Ossetia. The guerrillas attacked on the first day of the school year.Relatives of hostages wait for news near School No. 1 in Beslan.