On Sunday, the Republic of Congo will hold its second presidential election since the civil war, amid concerns that the vote could unleash a new round of civil unrest and conflict in the country.

This Sunday, incumbent president Denis Sassou-Nguesso faces 12 challengers in his run for a second seven-year term.

As of mid-June, there were 17 candidates, but four have since been disqualified by the Constitutional Court, including main opposition candidate, Ange Edouard Poungui. The former prime minister was rejected because he had not continuously resided in the country for the past two years, as required by law. He has said the decision was politically motivated.

Mr. Sasso-Nguesso has been president all but five years in the last three decades. He first took power in a 1979 coup before losing in a multiparty election in 1992. He seized power again in 1997 and won a landslide victory in the 2002 presidential elections from which key rivals were either banned or withdrew.

In the run up to this election, opposition members have accused the National Elections Organization Committee of bias and demanded its replacement. This is the same electoral committee that organized the country's 2007 parliamentary elections and 2008 local elections, which were denounced for fraud by observers from the African Union.

Four opposition candidates and one independent continue to call for Sunday's voting day to be moved because of concerns about the poll's organization, particularly with regards to voter records. The government says the vote will proceed as planned.

Previous elections have opened the door to violence and instability in the Republic of Congo, and for many Congolese those memories are simply too fresh. Bracing for Sunday's vote, some are setting money aside or leaving the capital Brazzaville altogether, where opposition candidates organized protests and a strike earlier this week.

In 1993, disputed parliamentary elections spiraled into bloody, ethnic-based fighting between pro-government forces and the opposition. Tensions flared up again in 1997, also an election year, eventually exploding into a full-scale civil war that killed thousands and displaced about a quarter of the population.

The National Security Council has sought to reassure the population. It says it plans to deploy 17,000 security staff members to protect polling stations, election rallies and candidates, including the current president.

The former French colony is one of Sub-Saharan Africa's main oil producers, though most of its population of four million people live in poverty.

If no candidate wins an outright majority Sunday, there will a second round of voting on a date yet to be announced.