Updated

As Ivory Coast prepares to complete its first presidential poll in a decade, the two candidates in Sunday's runoff called for an end to the violence that has marked recent campaigning.

Multiple clashes between the candidates' supporters in the last week have caused at least two deaths in a key battleground in the center of the country, stoking ethnic tensions right before a vote that could bring a peaceful closure to the world's largest cocoa producer's enduring crisis, or plunge it back into ethnic violence.

Interior Ministry Official Auguste Zoguehi said a man was killed in clashes in Oume, in the center of the country, on Friday. The previous night, Zoguehi had announced on state television that one man was stabbed to death by rival supporters in nearby Bayota.

That announcement came just minutes before President Laurent Gbagbo and rival Alassane Ouattara participated in one of the first live televised candidates' debates in African history.

Though both men called for calm, they each accused the other of involvement in political violence over the last ten years of conflict. Ouattara said that Gbagbo collaborated with the military putsch in 1999, while Gbagbo said Ouattara had a hand in a failed coup in 2002, which divided the country in two and led to an 8-year political standoff.

During the debate, Gbagbo announced a nationwide curfew at 10 p.m. the night of the vote to prevent any interference in vote counting, a decision his opponent said would only further heighten suspicions over the vote.

International observers say they fear large-scale violence if the loser refuses to accept the results.

"The runoff campaign is radicalizing and has taken on a tone that isn't without risks," Catherine Ashton, Vice President of the European Commission, said in a statement Wednesday, before calling on the political parties to calm down their supporters.

The United Nations said it will send an additional 500 peacekeepers and two military helicopters to reinforce its 9,800-strong peacekeeping mission for four weeks after the vote.

The Security Council also reiterated its Oct. 15 resolution which threatened sanctions against those who "obstruct peace and the electoral process and publicly incite hatred and violence."

"At this historic moment, we cannot allow ourselves to be taken over by negative sentiments," said U.N. mission chief YJ Choi.

In the last week, clashes between supporters of each candidate have spread across the country. Though they remain minor and isolated, they bring fears of what may come after the election results are announced.

On Wednesday, machete-wielding Gbagbo supporters built barricades in two impoverished neighborhoods in Abidjan to prevent Ouattara's campaign from holding rallies.

Security forces are being reinforced across the country, with rebel forces deployed alongside their regular army counterparts. Officials warned that they would act harshly against agitators.

"To those plotting in the shadows against peace, I tell you this: the armed forces of Ivory Coast will be merciless," army chief of staff Philippe Mangou said Monday in a televised statement.

Sunday's poll is the fruit of years of negotiations between Gbagbo and the rebels who still occupy the northern half of the county. Gbagbo has held on to power five years after his constitutional mandate expired and the elections were delayed six times before the first round was held Oct. 31.

The last delay was in February when Gbagbo dissolved the government and the electoral commission amid accusations that the electoral lists were being loaded with foreigners likely to vote for Ouattara. This led to three weeks of street rioting that left at least five people dead.

October's first round of voting was for the most part free and fair, with only minor irregularities, said international observers. The largest observation mission from the European Union, however, accused the Independent Electoral Commission of obstructing their teams and not allowing them to observe ballot-counting in several voting stations.

Gbagbo came out on top in the first round with 38 percent, followed by Ouattara with 32 percent. The other 12 candidates were dropped from the ballot for the second round, though the only one among them who received significant support was former president Henri Konan Bedie, who received 25 percent nationwide.

Since then, both campaigns have been concentrating on picking up Bedie's voters, who are concentrated in three regions largely populated by his Baoule ethnic group.

Ouattara visited a gathering of hundreds of Baoule chiefs in the capital Yamoussoukro, where he received an honorary Baoule title and asked for their support.

Gbagbo followed with a rally of Baoule chiefs in Sakassou, where he argued that Ouattara betrayed the Baoule when he was prime minister in the 1990s.

But Baoule voters have also been targeted with violence for their perceived reluctance to vote for Gbagbo.

Emile Kambou, a representative of the Ivorian Movement for Human Rights in Gagnoa, said that his organization had interviewed two people who were attacked by a group of Gbagbo supporters after being accused of voting for his opponents.

"Security forces are concentrated in the city and by the time they arrive in the villages, anything could have already taken place," he said.

A leaflet being circulated in the region calls on locals to kill Baoules in the region and chase the rest off.

"Let's prepare our guns, our machetes will be ready," the leaflet said. "Spread death for the service of our tribes, so we can confiscate the power."

Shortly after the first round, Bedie endorsed Ouattara and called on his supporters to "massively" support him, though it's not entirely certain that his voters will follow suit.

Gbagbo's campaign has been screening a video in town squares and villages across the country, which shows a rebel commander saying he received funding from Ouattara. While Ouattara has repeatedly denied any connection with the rebellion, the association has stuck and some Baoule voters hold him responsible for the civil war.

"I cannot vote for Ouattara, no matter what the Nana says," said Martine Kouassi, 68, referring to Bedie with the Baoule word for "chief."

The restaurant owner and mother of four from Gagnoa said she was in the north when the rebellion broke out and saw people chanting Ouattara's name on the streets.

"I'll never vote for someone who tore our country apart," she said.

Yet Kouassi has paid dearly for her support of Gbagbo. After asking a group of Ouattara supporters to stop handing out campaign literature in her restaurant, they threatened to burn it down.

Today Kouassi has two police officers posted outside of her restaurant to protect it, but said that even her regular customers don't dare come inside for fear of retribution.

Both courted and persecuted, the Baoule find themselves caught in the middle of an election that has pitted neighbors against each other and stokes the tribal tensions that risk ripping the country apart.

"Things will get better after the vote," she said, "I hope."