Police arrested and violently dispersed scores of pro-democracy activists on Monday protesting against controversial voting machines that the government wants to use in key elections later this year.
The pro-democracy movement Lucha (Struggle for Change) says the South Korean touch screen voting machines will pave the way for fraud in the long-delayed December 23 ballot.
Police detained 22 Lucha activists briefly in Kinshasa as they demonstrated outside the office of the national electoral commission (CENI), police said.
"They tried to march but were arrested by police. But there was no reason to hold them so I let them go," Kinshasa police chief Sylvano Kasongo said.
"Youths from Lucha came. They weren't scared and went right up to the CENI shouting 'No voting machines'," a street vendor told AFP.
"They did not resist arrest," another witness said.
In Goma, the capital of the restive Nord-Kivu province, police violently dispersed a Lucha protest beating several activists with batons, an AFP reporter said.
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"We have re-established order, about 20 youths were arrested," the city's police chief Colonel Job Alisi said.
"I had not authorised today's march and the police only did their job to re-establish order," Goma mayor Timothee Mwissa Kiense said.
In Bukavu, the main city in Sud-Kivu, 17 Lucha members were arrested but released an hour later, the group said.
"We were brutalised, beaten, tortured. Two of us were seriously injured... others were stripped of their money and cellphones," said Judith Maroy.
But police spokesperson Linda Margehane denied the activists were mistreated during their brief detention. Several activists were detained in other towns and cities, according to AFP correspondents.
The former Belgian colony has not seen a peaceful transition of power since 1960. The current president, Joseph Kabila, who has held office since 2001, has said he will not run again.
Several members of the UN Security Council, including Britain, France and the Netherlands, have said the UN was ready to offer logistical aid for the election but Kinshasa has rejected all offers of support.