A leading opposition candidate for president of Democratic Republic of Congo was questioned on Monday over government allegations of hiring mercenaries, a case that could halt his fledgling campaign in its tracks.
Moise Katumbi arrived at the prosecutor general's office in the second city Lubumbashi, dressed in a white suit and surrounded by supporters who chanted "President! Today is the day".
At least four people were arrested as hundreds of police tried to contain the crowds.
Katumbi has denied accusations made by the justice minister last week that he hired mercenaries including U.S. soldiers.
The enquiry could lead to charges that carry a prison term and could also tie Katumbi in legal knots that could derail his campaign to succeed President Joseph Kabila at elections scheduled November.
Many Congolese people say Katumbi is the strongest opposition candidate to succeed Kabila, given his personal wealth and popularity as the former governor of Congo's main copper-producing region. He also owns a soccer team.
Kabila is barred by the constitution from seeking a third term but has yet to announce his intentions. His ruling party has not named another candidate and the opposition says Kabila wants to delay the election to retain power.
Katumbi arrived at the prosecutor's office at about 10.15 a.m. local time (0815 GMT), accompanied by leaders of an opposition coalition that has backed his presidential bid, a Reuters witness said.