On Monday, clashes in the nearby city of Goma left four civilians and a policeman dead.
On Tuesday police sources said the 28 would be handed over to a military tribunal where they would face charges including "illegal possession of weapons".
Political tensions in the DRC are high after Kabila failed to step down on the expiry of his second and final term last December.
Police in the eastern Democratic Republic of Congo city of Beni said they had arrested nine demonstrators during a march Tuesday against President Joseph Kabila, a day after clashes in the region that left five dead.
The nine were "from Lucha," said Lisangi Nkumu, Beni's deputy police chief, referring to a pro-democracy group, Struggle for Change, which is campaigning for Kabila to leave office.
"They were demonstrating on the public highway without authorisation," he said. "They are being interviewed and will be handed over to the appropriate authorities."
Lucha campaigner Regina Masinda said that the police intervened shortly after the start of the march and "brutally" manhandled demonstrators who had their hands in the air and had sat down on the ground.
"Nine of us were arrested," Masinda said. "We demand their release."
On Monday, clashes in the nearby city of Goma left four civilians and a policeman dead, an AFP reporter said.
Twenty-eight people were arrested, two of them women, the police for North Kivu province said.
On Tuesday police sources said the 28 would be handed over to a military tribunal where they would face charges including "illegal possession of weapons".
"We have finished the questioning," Colonel Georges Kitungwa said, while an AFP reporter saw the suspects being loaded into a police vehicle.
"It's up to the military tribunal to judge these violations."
Political tensions in the DRC are high after Kabila failed to step down on the expiry of his second and final term last December.
Elections were due to take place this year under a transitional deal reached last New Year's Eve with the help of the Roman Catholic Church.
But the country's electoral commission says there will no vote before early 2019, mainly because of the problems of completing an electoral roll in the troubled central region of Kasai.
The uncertainty has stoked fears of a new eruption of political violence in a vast, poor country already struggling with ethnic divisions and fighting in its east.
Demonstrations have been banned or widely repressed since September 2016.
