SEOUL, DEC. 16 (WEDNESDAY) -- South Koreans headed to the polls this morning to choose a new president in the nation's first genuine election in 16 years.

Many Koreans hope that today's vote will mark a new era of democracy after decades of military coups and authoritarian rule. More than 90 percent of the nation's nearly 26 million voters are expected to cast ballots.

But the election-day mood was one of anxiety as well as hope, as voters worried about postelection violence and the potential instability of what is likely to be a minority government.

The South Korean military went on high alert to protect the nation from terrorism or attack from the north during the voting, officials said. Thousands of police were dispatched to guard polling and counting stations and to stand by for trouble in Kwangju and Pusan, strongholds of opposition candidates Kim Dae Jung and Kim Young Sam.

At the same time, thousands of university students fanned out from their campuses to monitor the voting and watch for government attempts to cheat, student leaders said. Christian and other dissident organizations mounted similar efforts, while delegations from a half-dozen American organizations also patrolled.

Some political analysts familiar with the latest public opinion surveys, which under South Korean law cannot be published, said Tuesday that ruling party candidate Roh Tae Woo appeared to hold a small edge as the campaign ended.

Roh, a former general and President Chun Doo Hwan's favored successor, was drawing strength from the division of antigovernment forces, whose two candidates spent the final day of the campaign attacking each other instead of Roh.

But the analysts also said the contest remains close. They said the winner is almost certain to garner fewer than 50 percent of the votes, which under South Korea's no-runoff law, will suffice for election but fall short of a mandate to unify the nation after a wrenchingly bitter campaign.

The winner will serve for a single five-year term.

Voters were reported going to the polls peacefully and in large numbers this morning, in sunny but very cold weather.

At a senior citizens' center in Sungnam City southeast of Seoul, more than 30 people were lined up outside to wait for a chance to vote. By 10 a.m., more than a quarter of the district's 3,200 voters had cast their ballots.

One 56-year-old office worker who voted for Kim Dae Jung said he felt proud to be casting a ballot again after 16 years. "I feel very happy to see the people's right has been restored," he said.

Allegations of vote buying surfaced early. An aide to Kim Dae Jung said party members in South Cholla Province had reported government officials were offering 50,000 won, about $63, to borrow identity cards that would allow proxy voting.

The final days of the campaign focused on allegations of fraud by the ruling party, as the opposition appeared to be laying the groundwork to reject a Roh victory.

"Our people will not condone the result of an unfair election," Kim Dae Jung said. "I sincerely hope there will be no reason for people to riot after the vote."

Many analysts said, however, that the talk of post-election uprisings helped Roh, who portrayed himself as the candidate of stability, law and order. Roh's hard-line warnings of chaos if the opposition wins appeared to have impressed many voters among the working class that Kim Dae Jung considers his natural constituency.

But supporters of Kim Dae Jung and Kim Young Sam called the election the nation's best chance to end decades of military dictatorship.

"I never went into politics before, but I think this is a very critical point in our history," said Hogan Yun, a former South Korean ambassador to the United Nations, in an interview. He endorsed Kim Young Sam.

The outcome of the election could influence future U.S.-South Korean relations. The United States has more than 40,000 troops here facing the communist north, and South Korea has become a major trading partner as well.

All four leading candidates said they would maintain close ties with Washington. All portrayed themselves as staunch believers in the kind of capitalism that has brought this nation two decades of remarkable economic growth. But the opposition parties, responding to growing nationalism among students and young voters, were more critical of what they called the dominant U.S. position in the partnership.

Many voters expressed relief that the campaign had ended. Results are expected Thursday morning. Although the official campaign lasted only one month, today's election capped years of combat between Chun's government and the nation's opposition.

Chun, who took power with Roh's help in a 1979 coup, had promised from the start to become South Korea's first chief executive to step down voluntarily when his term expires in February.

But Chun's original plan to anoint Roh as successor foundered as widespread street protests erupted in June.

Chun agreed to allow a direct election and other reforms. Political prisoners were freed, restrictions on the media were loosened and the nation began debating its future with an openness that was almost unimaginable one year ago.

Roh appeared to face an almost impossible task of persuading voters to forget his intimate connections to a man who even his supporters acknowledge is an unpopular incumbent. But when the two longtime opposition leaders, Kim Young Sam and Kim Dae Jung, both insisted on running, Roh's challenge suddenly became more manageable.

The two Kims mostly refrained from criticizing each other during the campaign, but at the close, Kim Dae Jung attacked his former ally for printing thousands of pamphlets claiming Kim Dae Jung had withdrawn from the race.

Kim Dae Jung demanded that the other Kim apologize for the "very immoral act" and withdraw.

By early October, four leading candidates had emerged: Kim Dae Jung, the charismatic and savvy opposition leader from the economically disadvantaged region of Cholla; Kim Young Sam, who portrayed himself as a moderate centrist who could take power without provoking the powerful military or the well-organized student activists; Roh Tae Woo, who served faithfully as Chun's right-hand man in a series of Cabinet-level jobs during the past seven years; and Kim Jong Pil, a prime minister in the pre-Chun regime of Park Chung Hee.