The Central Election Commission (CEC), meanwhile, quit counting ballots for the day with 5.6 percent of the polling places still to report and the two leading candidates within one percentage point of each other.
With 94.4 percent of the precincts counted, Prime Minister Viktor Yanukovych had 40.12 percent of the vote and opposition leader Victor Yushchenko had 39.15 percent.
The opposition leader led in 17 of Ukraine’s 26 regions, including the capital, Kiev, where most of the uncounted ballots were cast. Mr. Yanukovych led in the remaining nine regions, mostly in the largely industrialized, Russian-speaking east.
Because neither candidate won 50 percent of the vote, the two will meet again in a runoff on Nov. 21.
Oleksander Zinchenko, Mr. Yushchenko’s campaign manager, accused the CEC of stopping its count for fear that the remaining Kiev ballots would have put his candidate ahead.
“It’s understood how Kievites voted. And then the CEC would be forced today to say that Yushchenko won the election. That’s why the CEC needed to take a pause, to figure out what to do now.”
Bruce George, a special coordinator for the Organization for Security and Cooperation in Europe, which sent 600 observers to Ukraine, said the election had failed to meet “a considerable number of OSCE, Council of Europe and other European standards for democratic elections.”
Many of the violations concerned electors’ names not appearing correctly on voter lists or other technicalities, such as their names being misspelled. Some Ukrainian lawmakers said the mistakes affected 30 percent of voters.
Natalia Plotnyk, a resident of Kiev’s affluent Pechersk region, was nearly denied the right to vote because her family’s last name appeared on the voter list using the Russian transliteration, rather than the Ukrainian.
Elections officials allowed Miss Plotnyk’s mother to vote, but said she could not. It was only after she involved senior election officials and neighbors vouched for her identity that Miss Plotnyk was allowed to cast her ballot.
In other regions of Ukraine, many voters waited for hours to win court approval to vote because of similar problems.
U.S. federal Judge Bohdan Futey, an observer with the International Republican Institute, said such incidents marked “a step back” for Ukraine’s democracy.
“This didn’t happen before,” said Judge Futey, referring to Ukraine’s two previous presidential elections, which received high marks. “The government needs to take immediate steps” to resolve these issues before the second round.
But observers from Russia and the Commonwealth of Independent States said Ukraine’s race was free and fair. So did a group of former U.S. congressmen who visited 75 polling places in Odessa, Donetsk and Kiev.
“The elections took place within the framework of the law,” said Bob Carr, a former Democratic congressman from Michigan, according to the Unian news agency. “They were transparent and the violations that were reported don’t put in doubt the wishes of the voters.”
Mr. Yanukovych, who welcomed the results from Sunday’s race, said it was important to rectify issues before the runoff.
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