Police in the capital Kinshasa clashed with an opposition march on Saturday, firing tear gas at hundreds of protesters.
The police said they had deviated from the authorised route through the city.
The march was organised by opposition leaders against what they say are irregularities when people try to register to vote for the presidential elections scheduled for December.
The protesters are also angry at the high cost of living and accuse President Felix Tshisekedi of being corrupt.
"Life has become untenable, look how the volume of bread has dropped significantly. We are calling for change in Congo, social change," said Bindanda Bilisi, a father of six.
Moise Katumbi, a millionaire businessman and a former governor of Katanga province, who is expected to run in the presidential election in December, fell out with Tshisekedi when the former president Joseph Kabila was in power.
"It's sad, you see they are shooting with tear gas, at the beginning it was with real bullets. And all this is Mr. Tshisekedi, it's very sad, we were with him in the opposition and if they don't even have to respect the Congolese people who want to march because there is the high cost of living, nothing is working in the country, there is corruption, it's sad," he said, whilst on the march.
This demonstration was organised by Katumbi, Martin Fayulu who was a presidential candidate in the 2018 which he claims he won, the former Prime Minister Augustin Matata and MP Delly Sesanga.
The clashes began when dozens of riot police arrived in their vehicles, began to fire tear gas and arrested at least a dozen people.
Later Congolese Human Rights Minister Albert-Fabrice Puela condemned "acts of repression" and "brutality" against demonstrators, including "minors", in a statement. “We demand urgent investigations from justice so that responsibilities are established on the various violations” observed, he added.
Prevented from advancing by the police, the opposition leaders were stuck in their vehicles.
“It is a peaceful march, to protest against a chaotic electoral process which prepares President Tshisekedi to take power by force, against the high cost of living, against oppression”, detailed the former Prime Minister Matata.
The commander who led the police operation disagreed.
“The march is authorised” but on the “other side” of the city, in the northwest," Faustin Numbi said.
"We spoke with them, telling them to clear the road and go to the starting point which is located in Mbeseke. They did not want to comply," he added.
On this route, another group of demonstrators was framed by the police before being dispersed when they wanted to move towards the seat of parliament, noted an AFP correspondent.
At a joint news conference, the protest organisers said at least two injured protesters were "between life and death". They also announced the holding of a new demonstration on Thursday in front of the headquarters of the National Electoral Commission in Kinshasa.
The presidential election is scheduled for December 20th. President Tshisekedi, who came to power in 2019, is seeking re-election.