(Bloomberg) -- Democratic Republic of Congo opposition leader Martin Fayulu will go to court to challenge results that showed he lost last month’s presidential election.

Fayulu claims results showing rival opposition candidate Felix Tshisekedi won the Dec. 30 poll were rigged and has urged his supporters to protest against them. Fayulu topped an opinion poll before the vote, and Western diplomats have said a large-scale observer mission run by the country’s influential Catholic Church found he garnered the most votes.

“We will introduce an appeal to the Constitutional Court,” Eve Bazaiba, a spokesman for Fayulu, said by phone Friday from the capital, Kinshasa.

Congo is preparing for its first-ever transfer of power via the ballot box, bringing an end to President Joseph Kabila’s 18-year rule. The result, which the Constitutional Court has yet to validate, confounded expectations that Kabila’s protege, Emmanuel Ramazani Shadary, would win.

To contact the reporter on this story: William Clowes in Kinshasa at wclowes@bloomberg.net

To contact the editors responsible for this story: Antony Sguazzin at asguazzin@bloomberg.net, Paul Richardson, Karl Maier

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