At least two people have been killed and more than 40 injured after police attacked opposition supporters at a rally in the Democratic Republic of Congo second-largest city of Lubumbashi, rights activists say.
Fifteen supporters of main opposition presidential candidate Martin Fayulu had bullet wounds, they say.
Police deny anyone was killed but say two people were injured.
DR Congo is holding delayed general elections on 23 December.
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President Joseph Kabila is set to step down after 17 years in power. His mandate ended in 2016 but he defied internal and external pressure to leave office.
He recently told the BBC that he wants to oversee a peaceful poll.
Mr Fayulu, 62, was chosen as the main candidate for the opposition coalition to face Emmanuel Ramazani Shadary, the ruling party candidate and a loyalist of outgoing President Kabila.
Felix Tshisekedi, another opposition leader, is also in the running.
Police disrupted the opposition rally on Tuesday by using water cannon and opening fire.
“We have seen that the authorities have recruited young people, and sent them to provoke scuffles with opposition supporters, in order to then justify the forceful intervention of the police, and to paralyse the activities planned by Martin Fayulu. We condemn it,” Georges Kapiamba, from the The Congolese Association for Access to Justice (ACAJ), said.
Mr Fayulu tweeted photos of himself taking refuge in a vehicle during the police operation, blaming Mr Kabila for being behind it.
A t-on encore besoin de preuve de la barbarie du régime de Mr Kabila? Il peut tout faire, mais il est déjà vaincu. pic.twitter.com/qEA7yqzc8O
— Martin Fayulu (@MartinFayulu) December 11, 2018
Mr Fayulu called off another rally in Kindu in eastern DR Congo after clashes broke out between his supporters and those of the governing coalition candidate.
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A woman was killed on Wednesday in the western town of Kalemie after police fired tear gas to disperse opposition supporters, news agency Reuters reports.
Opposition coalition Lamuka, which is backing Mr Fayulu, said the police crackdowns “show clearly that President Kabila and his team realise that… they are going to lose the elections”.
Mr Fayulu is a well-known businessman who worked for US oil giant Exxon Mobil for two decades, taking up positions in several African countries from 1984 to 2003.
He went into politics in 2016 and is currently a member of parliament.
He is campaigning on a promise to restore the rule of law and security in the conflict-ridden country.
Source: BBC