BELGRADE, Yugoslavia (AP) - After an election Sunday marked by a large turnout and allegations of fraud, Yugoslavia's once struggling opposition claimed victory and urged Slobodan Milosevic to peacefully quit power after 13 years of hardline rule.
Milosevic, however, showed no signs of conceding defeat. His spokesman, Nikola Sainovic, told reporters early Monday he doubted there would even be a need for a run-off vote - required if no candidate gets more than 50 percent - because ''our candidate is leading.''
The state election commission closed up for the night without announcing any official returns. Voting - in which the turnout was estimated at higher than 70 percent - was plagued Sunday by reports of blatant irregularities by Milosevic backers, including ballot box stuffing, the few domestic monitors watching the polls said.
Still, two rival opposition parties said Milosevic was trailing his strongest challenger, Vojislav Kostunica, and that the best the Yugoslav president could hope for was to head into a runoff Oct. 8. They based the claims on counts by their own vote monitors.
''According to our count, the first-round victory is certain. Dawn is coming to Serbia. I'm excited,'' Kostunica said early Monday. ''I'm happy for the people and the country because it's almost the last moment to take the destiny in our hands. There is much work ahead.''
''There is no doubt that we overwhelmingly won on all levels,'' said opposition campaign manager Zoran Djindjic. ''Milosevic has to seriously understand the judgment of history, and he shouldn't gamble any longer. He has to recognize the defeat. It seems, this is the end of his career.''
Confident of victory by an opposition that seemed hopelessly fragmented only months ago, huge crowds streamed into the streets of downtown Belgrade late Sunday to await official results. Helmeted riot police carrying shields and armed with tear gas launchers cordoned off the group but later withdrew after a concert by Milosevic's supporters ended.
Similar gatherings were reported in Nis, Novi Sad, Cacak and several other towns in Yugoslavia's main republic Serbia. There were no reports of clashes, and early Monday the crowds in Belgrade were returning home.
With no offical word on results, Western governments held late night consultations to determine how to respond if Milosevic rigs the count.
In Washington, the State Department warned that ''the world is watching these elections and the response of the authorities in Belgrade very closely.''
In the voting, ''large numbers of the population ... expressed their wishes in an election where the choice was clear,'' spokesman Richard Boucher said. ''We congratulate the people of Yugoslavia on their commitment to democracy.''
Sainovic, who like Milosevic is under international indictment for war crimes, disputed the opposition claims of victory. He claimed that with 20 percent of the votes counted, Milosevic was leading by 44 percent while Kostunica had 41 percent.
Those figures were different from those posted on the party's own web site, which showed Kostunica leading with 44 percent to 41 percent for Milosevic.
Cedomir Jovanovic, spokesman of Kostunica's Democratic Opposition of Serbia, said that based on returns from 45 percent of 10,000 polling stations, Kostunica was leading with 57 percent to 33 percent for Milosevic. Three other candidates are in the race.
The ultranationalist Serbian Radical Party, Milosevic's partner in Serbia's government, reported Kostunica leading Milosevic by 53.5 percent to 37.9 percent with about 20 percent of the votes counted. The party admitted its own candidate was defeated.
The United States - which has invested millions of dollars in an attempt to organize the traditionally fractured Serbian opposition - has made ousting Milosevic a major goal, believing there can be no stability in the Balkans so long as he remains in power.
The stakes were especially high in the voting, which also included selection of a new parliament and municipal governments.
If Milosevic loses, he risks extradition to the U.N. war crimes tribunal in The Hague, Netherlands, which indicted him last year for atrocities committed by his troops in Kosovo. He may also risk massive revenge by Yugoslavs tired of being an impoverished pariah country after a decade of his rule.
The European Union has promised massive aid to Yugoslavia if Milosevic loses. Montenegro, the smaller republic that along with Serbia forms present-day Yugoslavia, said it would hold an independence referendum if Milosevic wins.
Kostunica had been leading in opinion polls despite a campaign marred by a crackdown against opposition supporters, one-sided coverage by the staunchly pro-Milosevic media and the lack of broad-based foreign monitoring.
The Center for Free Elections and Democracy, a private group including human rights workers, lawyers and other volunteers, reported a turnout of 74.6 percent in Yugoslavia's main republic Serbia.
In the smaller republic of Montenegro - where the pro-Western government boycotted the vote - the turnout was only about 24 percent, the opposition said.
Milosevic made no statement about the seemingly unfavorable returns. Earlier Sunday, he brushed aside accusations that he would rig the vote to stay in power, predicting prosperity after he wins and his troubled country is ''cleared up'' politically.
The president's statement, made after he cast his ballot in the Dedinje district where he lives, may indicate he plans to crack down hard on political opponents - whom he has dubbed NATO lackeys and traitors - if he's declared the winner.
The Center for Free Elections and Democracy reported major voting irregularities. They included opposition representatives being kicked out of polling stations or not allowed to inspect voters' lists, voting boxes and ballots.
At many voting places, police were present in front of polling stations, and there was public - instead of secret - voting in southern regions of Serbia, according to the center, a nongovernmental organization which included human rights activists, lawyers and other pro-democracy volunteers.
In the eastern town of Negotin, opposition representatives were banned from a polling station but managed to get in by force, only to find that the ballot boxes had been stuffed in advance with ballots for Milosevic, the Belgrade-based group said.
''There is an absolute mess in Serbia today,'' said Marko Blagojevic from independent monitoring group. ''I don't think elections like this were ever held anywhere, ever since the Stone Age.''
The government's electoral commission said the vote passed without irregularities, ''despite Western propaganda.''
Sainovic claimed Milosevic won ''overwhelmingly'' in Kosovo. However, the chief U.N. administrator in the province, Bernard Kouchner, said the ''so-called elections did not meet any international and European standards in terms of democracy.''
Most of the examples cited by the monitoring group could not be confirmed. However, in Kosovo, Western reporters saw cases where polling stations were never opened, where prominent opposition members were told their names were not on registration rolls or where voters had no privacy to mark their ballots.
Others were turned away because their names did not appear on registration lists. Officials claimed that was a result of the turmoil that swept Kosovo during last year's conflict, which ended with the arrival of NATO-led peacekeepers.