“Eleven people died in Kinshasa and one in Kananga,” Jonas Tshombela, a spokesman for the protest organisers, told AFP.
Catholic and opposition groups on Sunday defied a ban on demonstrations demanding that President Joseph Kabila leave office.
They were met with a deadly crackdown by authorities, who fired tear gas into churches and bullets in the air to break up gatherings.
The protests took place on the first anniversary of a deal under which Kabila was scheduled to leave office in 2017 after fresh elections — a vote that has since been postponed until December 2018.
In contrast to the toll given by the protestors, the United Nations said in a statement Tuesday that “at least five people” were killed, adding that several others had been wounded and more than 120 arrested. On Sunday, a UN source said eight were killed and 123 arrested, including priests.
An AFP reporter at a demonstration in the central city of Kananga saw a man shot in the chest by soldiers who opened fire on worshippers.
Police spokesman colonel Rombaut-Pierrot Mwanamputu, meanwhile, said in a statement on Tuesday that “no deaths” had occurred in the context of the demonstrations.
On Sunday, he had said three civilians — “robbers” and “looters” — had been killed, in incidents that had occurred far from the protests. The DRC authorities also say a policeman was killed when a police station came under “attack.”
Meanwhile, the internet was restored on Tuesday after the government cut services for three days.
The Congolese minister for telecommunications, Emery Okundji, ordered mobile operators to cut internet and SMS services “for reasons of state security” on Saturday.
Internet cuts are common during anti-government demonstrations in the vast, mineral-rich central African country.
Protesters want Kabila to promise he will not further extend his time in power in DRC, a mostly Catholic former Belgian colony.
In its statement on Tuesday, the UN reiterated its appeal to “all Congolese actors” to adhere to the December 31, 2016 agreement — “the only viable path to the holding of elections, the peaceful transfer of power and the consolidation of stability in the DRC.”