By Aaron Ross and Christian Elion
BRAZZAVILLE (Reuters) - Congo Republic President Denis Sassou Nguesso on Friday urged voters to deliver a "knock-out blow" to opposition candidates in Sunday's election by giving him an outright majority that would extend his long rule.
Sassou Nguesso, who has led Congo for 32 of the last 37 years, pushed through constitutional changes last October to remove term and age limits that would have prevented him from seeking re-election.
He ran on an ambitious agenda focused on job creation and infrastructure development, telling a rally in the capital, Brazzaville, on Friday that his restoration of peace after a bloody civil war in 1997 has allowed the economy to grow.
"Everywhere the people have expressed their satisfaction about the infrastructure we have built," he said. "On March 20, vote for your candidate and it will be a knock-out blow."
An outright majority on Sunday would avoid a run-off with opposition candidates. But it would also be a setback to democratic transition in Africa, where a number of countries have had leaders in place for decades, analysts say.
Presidential candidate Andre Okombi Salissa said on Friday the opposition has documented preparations for widespread vote rigging, including voters registered at multiple polling sites, individuals with multiple voter cards and the distribution of voter cards to non-citizens.
The government rejects the accusations and says its opponents are stirring up post-election chaos. The opposition in turn denies it is inciting violence but warns that people will not accept a tainted result.
"It is not possible for President Sassou to win these elections," said retired General Jean-Marie Mokoko, who joined Salissa and Guy Brice Parfait Kolelas at the news conference. "Everywhere we have traveled there has been a total rejection."
At least 18 protesters were killed before the October referendum, which the president's critics say was rigged after the constitutional changes were approved by 93 percent of voters.
Eight opponents are running against Sassou Nguesso, including Mokoko, who once served as the president's security adviser. Five of them have promised to support the president's opponent in any run-off, although say an opposition win is unlikely because the electoral commission is biased.
Five of the eight have created their own electoral commission to monitor the official body, which they say answers to the president. The European Union decided not to send observers, saying recent changes to the electoral law lacked transparency.
Sassou Nguesso ruled the country from 1979 to 1992 and from 1997 until now, including disputed election victories in 2002 and 2009. His critics say the country's oil wealth has enriched a small elite, pointing out around half of the population lives in poverty.
Oil companies including France's Total, Italy's ENI, London-listed Tullow and the U.S. company Chevron operate in Congo, making western governments less willing to rock the boat, analysts say.
"Western powers have been relatively silent on Sassou's third-term aspirations, in part because of more entrenched economic interests in Congo," said Christoph Wille, a Congo analyst at Control Risks.
(Editing by Matthew Mpoke Bigg and Larry King)