(Adds comments by president, details on regional bloc delegation expected in Abidjan)
By Ange Aboa
BOUAKE, Ivory Coast, Oct 16 (Reuters) - Ivory Coast President Alassane Ouattara rejected calls for negotiations on Friday from rivals urging a boycott of an Oct. 31 election they say he should not be standing for.
Ouattara's main challengers, ex-President Henri Konan Bedie and ex-prime minister Pascal Affi N'Guessan, accuse the 78-year-old former International Monetary Fund (IMF) economist of violating the constitution by standing for a third term.
Protests against Ouattara's candidacy have killed more than a dozen people since August.
Thousands of cheering supporters greeted Ouattara in Bouake, the capital of the rebel-controlled region of the country that swept him to power in 2011 after a disputed election, as his convoy sped into town to officially launch his campaign.
"They are afraid of losing the election. As we say in Ivory Coast, if they are men enough, they should participate in the elections," Ouattara told the rally.
The opposition has called for the election to be postponed, and a fresh date set for new election in which Ouattara will not be a candidate.
"The dialogue has already happened. Let's go to elections. There won't be any delay," Ouattara, who is widely considered the election favourite, told local chiefs earlier in the day, adding he would not accept international mediation.
"No one is coming here to negotiate anything."
However, a crisis prevention mission of the West African regional bloc ECOWAS is expected in Abidjan on Sunday, the bloc said.
This year's election is a test of stability for Ivory Coast, the world's top cocoa producer. Ouattara's victory in the 2010 election led to a brief civil war that killed 3,000 people after incumbent President Laurent Gbagbo refused to concede.
Ouattara's decision in August to run again after initially saying he would not has stirred frictions. He disputes the opposition's claims that he cannot run again, arguing a new constitution approved in 2016 reset his two-term limit.
Affi and Bedie reiterated their calls for a boycott on Friday, urging civil disobedience to block election rallies and the distribution of voting cards.
"We will fight until the end because our combat is just," Affi told supporters in Abidjan. (Reporting by Ange Aboa and Loucoumane Coulibaly in Bouake Writing by Aaron Ross and Bate Felix; Editing by Andrew Cawthorne and Matthew Lewis)
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