BELGRADE, Yugoslavia - About 2 this morning, just hours after more than 200,000 people demonstrating support for Vojislav Kostunica went home, the government of Slobodan Milosevic suddenly announced that both candidates would have to meet in a second round of presidential elections Oct. 8.
This decision of the government-controlled federal election commission, which had been expected tonight, was a shock to the political system and showed that Milosevic would not leave office without a fight.
It is likely to provoke anger here once people wake and a new and explosive round of street demonstrations from Kostunica's supporters, who believe he won the election with more than 50 percent of the vote in the first round.
Kostunica has vowed to boycott a second round and held out hope that the commission would recognize his outright victory. In an interview yesterday, he said of Milosevic, "I think there is now no way out for him. This is a situation that cannot last long."
"People know I won these elections," Kostunica said. "Why should I accept Milosevic's offer of a second round? People won't understand it and will feel that I'm betraying them."
Last night, to the massed and happy crowd, Kostunica said: "We tell them from this place that there is no second round. There is no market in votes."
In the announcement of the middle of the night, the electoral board said, "Based on the final results from 10,673 polling sites, presidential candidate Vojislav Kostunica won 2,474,392 votes, or 48.96 percent, and Slobodan Milosevic 1,951,761 votes, or 38.62 percent."
Therefore, it said, the second round of voting would go ahead.
"This is not a decision but a joke," Zoran Djindjic of the Democratic Opposition of Serbia said of the plan.
Milosevic has been silent since the vote Sunday, making no appearances of any kind.
The size of the crowd in Belgrade last night - one of the largest in memory here - was a message to Milosevic, too, backed by other large rallies in such towns as Novi Sad, where 35,000 gathered, and Nis, with 25,000. In addition, 15,000 rallied in Kragujevac and 10,000 in Kraljevo.
Before the commission announcement, Western governments were passing the word to Milosevic that his options were fast running out, senior Western officials said in telephone interviews.
They told Milosevic through intermediaries that he had a few days to renounce power and leave the country without difficulty, to settle where he would, but that if he delayed, he could face arrest and a trial in The Hague on war crimes charges.
"His choice is to fight or make a graceful exit," a senior Western official said. "His only hope of avoiding The Hague is to say, publicly and irrevocably, that he's leaving." If he leaves, Russia and Belarus appear to be possible destinations.
No Western country would publicly bless this arrangement, the officials stressed, given Milosevic's indictment by the war crimes tribunal in The Hague, a creation of the United Nations Security Council.
"But there are enough people indicating, to the extent he's listening, that he has a little time to make a dignified exit without interference," another senior Western official said. "We want him to hear it loud and clear."
The representatives of a number of Western nations left Belgrade before the NATO bombing began last spring, and from a distance they have been lobbying the Serbs to overturn Milosevic, with offers to end economic sanctions and provide aid.
In his interview, Kostunica said Milosevic could cling to power now only through repression. "Politically he has no future, and I'm not sure he can count on repression, either," he said.
Kostunica told the crowd he was sure of his victory, given their strength, and he had a message for the army and the police, who did not interfere last night.
"Our message to the army and the police is that we are one," he said. "The army and the police are part of the people; they exist to protect the people, not one man and his family."
As the crowd shouted, "He's finished!" about Milosevic, Kostunica asked, "Why would our army, which was so courageous last year against NATO, be afraid now of one man?"
People in the crowd were happy but slightly unsure that Milosevic was beaten. There was a sense of self-discovery and suspense, caught in a historical tide that had not yet reached its peak.
"I believe he's finished, because of the people here," said Ivana Petrov, a 25-year-old medical student. "We hope he'll go. But he won't go so easily. Things here can't change that fast, even if he does go."
Vladimir Panic, a 22-year-old economics student, said: "I think that finally we'll win." How quickly? "It's going to be tough," he said. "People will have to go out onto the streets for many days."
For Milosevic, calling the elections was a blunder; his term extended to next July, but he called the election early, apparently hoping to cement and extend his hold.
Gen. Nebojsa Pavkovic, the army chief of staff who supports Milosevic, gave an interview in which he said the army would stay out of politics.
He said Milosevic "will never order the army to intervene against the people" and the army would "respect the choice" of Yugoslavs in the presidential election.