Police in Kinshasa banned all campaign rallies on Saturday after rival supporters hurled rocks at each other and at least one person was reported dead as tensions rose two days before presidential and parliamentary elections.
Riot police in the Congolese capital used tear gas to disperse a political gathering in the city centre and one person was injured as presidential guard members fired shots to clear opposition supporters from the airport, Reuters reporters said.
Asked to confirm the ban, Kinshasa police chief Jean de Dieu Oleko told Reuters: Yes, all of them.
President Joseph Kabila and his two main rivals, Etienne Tshisekedi and Vital Kamerhe, had been due to hold rallies within several hundred metres of each other later on Saturday.
Kamerhe told Reuters four people were killed in Kinshasa on Saturday, including one of his supporters, but it was not immediately possible to confirm that toll.
Jacquemain Shabani Lukoo, secretary-general of Tshisekedi's UPDS party, said their event would continue as planned.
It is Kabila who has cancelled his meeting. We are carrying on with our meeting, Shabani said.
However a Reuters reporter at Kinshasa's N'djili airport saw police preventing Tshisekedi from leaving the airport to travel into town for the planned rally.
Citing health and security officials, a United Nations source said at least one person had died but there was no official confirmation of the death or its circumstances. A Reuters reporter saw a lifeless body on the road to the airport.
It was the latest sign of tension in the run-up to Congo's second presidential election since a 1998-2003 war, a poll which has been marked by opposition allegations of irregularities and concerns about inadequate preparations.
Despite a logistics operation supported by helicopters from South Africa and Angola, it is not clear whether all the ballot slips will have reached the 60,000 voting stations by Monday in a country two-thirds the size of the European Union.
Tshisekedi said earlier he could accept a delay but only if the head of the national election commission, whom he accused of having political ties with Kabila and turning a blind eye to alleged irregularities, was sacked.
I would agree (to a delay) if that meant a more credible, democratic and transparent process, the 78-year-old veteran opposition leader told French RFI radio.
But one thing is clear: if we say there will be a delay, it is clear that the election commission cannot be led by Daniel Ngoy Mulunda, he said, accusing him of having been a founding member of Kabila's PPRD political party.
Mulunda, who will have the deciding vote if his commission is split on any election dispute, said this week he did not deny having been a member of the delegation that accompanies Kabila on foreign trips, but said he was not a founding PPRD member.
Tshisekedi alleged the existence on paper of fake polling stations to allow vote-rigging, a claim authorities have denied. His party also accuses Kabila of using state media and transport assets in the service of his campaign.
Kamerhe said the Congolese would not accept a rigged poll.
They want free and fair elections that allow them to take their destiny in their own hands. People will refuse cheating wherever it takes place, he told Reuters surrounded by chanting and dancing supporters at his party headquarters.
One election observer said authorities had said ballot slips for an electorate of 32 million eligible voters had arrived at regional so-called sub-hubs but added this did not guarantee they would reach often remote polling stations.
We are a long way off, said the observer, who declined to be identified.
For many Congolese, there was a last-minute scramble to find out where they should be voting. Gervis Ilunga, a 44-year-old security guard, said he registered in one Kinshasa district but ultimately found his name elsewhere.
In 2006, things were at least organised, he said of the first post-war poll largely organised under the auspices of the United Nations. It is not like that this time ... There will be too many challenges this time.
Under constitutional amendments signed off by Kabila this year, the presidential vote will be decided in a single round, meaning the winner can claim victory with a simple majority. Analysts say that favours Kabila against the split opposition.
Blessed with lucrative resources of copper, cobalt and precious metals, Congo remains plagued by poverty and insecurity, especially in its rebel-infested east where a simmering low-level conflict persists.
(Additional reporting by Finbarr O'Reilly; Writing by Mark John; Editing by Sophie Hares and David Cowell)