Moise Katumbi, a prominent opposition leader in Democratic Republic of Congo, said on Wednesday he would run in November's presidential election when incumbent Joseph Kabila is due to step down in accordance with the constitution.
Kabila's opponents say he is trying to cling to power beyond his mandate and Katumbi's declaration could heighten political tension, given that the president has yet to announce his plans.
More than 40 people were killed in protests in January 2015 over alleged attempts by Kabila to delay the presidential vote to remain in office.
"I accept with humility this heavy responsibility," Katumbi said in a statement posted on his official Twitter account, referring to his nomination for the presidency by three opposition coalitions in recent weeks.
The election will likely be delayed since the election commission says updating voter rolls will take about 16 months.
Katumbi is a multimillionaire and former governor of Katanga, a copper mining region. His announcement had been expected for months but was delayed as he tried to win support from a fractious opposition.
Katumbi governed Katanga from 2007 until last September when he quit Kabila's party, accusing it of plotting to extend the president's rule, which began in 2001.
Wednesday's declaration appeared to be aimed at showing he would not bow to political pressure. Tensions have risen in recent weeks between Katumbi's camp and the government.
In April, police used tear gas to disperse a rally led by Katumbi in the country's second-largest city, Lubumbashi, and arrested four of his bodyguards.
On Wednesday, Justice Minister Alexis Thambwe ordered a probe into Katumbi's alleged recruitment of mercenaries. The government "has proof of ... Katumbi's involvement in the recruitment of mercenaries, including several retired American soldiers," he said.
In his statement on Twitter, Katumbi replied: "The low blows of the government do not hinder my peaceful combat. I will be the candidate of the rule of law."
Katumbi has yet to win the support of the largest opposition parties, including Etienne Tshisekedi's Union for Democracy and Social Progress. Katumbi said in the statement he would soon begin a national tour to develop a common opposition platform.
Congo has never undergone a peaceful transition of power.
The former Belgian colony was ruled for decades by Mobutu Sese Seko and since then eastern Congo has been plagued by war and instability.