ASTANA, Kazakhstan, Dec. 4 - The election for president in Kazakhstan passed peacefully on Sunday, and early signs indicated that President Nursultan Nazarbayev, the former Communist boss who has governed this country since it declared independence from the Soviet Union, was heading to a landslide victory over four opponents.

Opposition candidates contended that there was vote fraud, but suggested that they would not hold public protests or mass actions in this enormous Central Asian state, underscoring the strength of Mr. Nazarbayev, whom they have tried to portray as authoritarian and unfailingly corrupt. The opposition said it would prepare legal challenges instead.

Mr. Nazarbayev, 65, has dominated Kazakh political life since the last years of the Soviet Union.

He has been accused in federal court documents in New York of receiving millions of dollars in bribes from an intermediary representing American oil companies seeking rights to Kazakhstan's oil fields, in a case against an American businessman under the corrupt practices act. But he has also maintained popular support even as his critics have struggled to circulate word of the accusations in a nation in which the independent news media are severely restricted.

The president's supporters say he has tightly managed Kazakhstan's politics and oil-dominated economy, moving it from the dysfunction of the Soviet period to relative prosperity in recent years, and without the war, ethnic strife, disorder and outright dictatorships that have marked Central Asia since Communism's collapse.

Preliminary election results were expected to be released Monday; early data of a survey of voters leaving the polls indicated that Mr. Nazarbayev had received nearly 85 percent of the vote. Although the reliability of the poll could not be immediately determined, it seemed roughly consistent with the sentiment in the capital, where a preponderance of voters interviewed Sunday expressed eagerness to keep him in office.

"I trust him, because I see the changes in our country, and they are positive," said Arai Ospanova, 19, a university student, after casting her ballot here in the capital on the Asian steppe.

Kazakhstan, however, has never held a free and fair vote, and there have been ample signs that the latest presidential campaign was marred by abuses of state resources, restrictions on freedom of assembly and speech, and election-day fraud.

The Organization for Security and Cooperation in Europe, which has provided the principal election observation mission, was scheduled to release its preliminary report on the election on Monday.

The organization's pre-election reports have noted, among other shortfalls, that Kazakh newspapers have been shut down or seized, television coverage has favored the president, and there have been complaints of intimidation and beatings of opposition supporters.

Perceptions of the election have also been undermined by the fatal shooting last month of a former Nazarbayev loyalist who had become a prominent opposition figure. He was found dead at his home in Almaty with two gunshot wounds in the chest and one in the head. The police officials have suggested that the death was a suicide.

Kazakh officials, while acknowledging that the country is still developing and civil society remains nascent, were lobbying for a favorable election report from the monitors, hoping to enhance the nation's credibility as it seeks tighter integration with the West.

"I hope that the final report will be objective and without any double standards," Onalsin I. Zhumabekov, chairman of the Central Election Commission, said in an interview.

Voter turnout was high, exceeding 75 percent of Kazakhstan's nearly nine million voters, according to the election commission's preliminary results.

But there were suggestions that turnout was manipulated, as voters were seen by observers and journalists receiving gifts from poll workers, including theater tickets, electric teapots, mixers and hair dryers. Mr. Zhumabekov said Kazakh law did not prohibit such practices.

"I do not see this as any attempt at interference," he said, adding that it helped lure voters to polling places. "Let them do it. It is good."

The opposition also claimed that there were organized efforts at multiple voting, with the result of inflating the turnout.