Riot police used tear gas to disperse hundreds of protesters in the Congolese capital Kinshasa on Saturday as campaigning by rival groups drew to a close two days before presidential and parliamentary elections, Reuters reporters said.

There were bouts of rock-throwing between opposing supporters and brief bursts of gunfire, the reporters said. Citing local 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.

President Joseph Kabila and two of his main challengers, Etienne Tshisekedi and Vital Kamerhe, were all due to hold campaign rallies within several hundred metres of each other later on Saturday.

The stand-off between riot police and protesters took place near the central Kinshasa stadium where Kabila was due to appear. There were no immediate reports of injuries.

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 that voting arrangements will not be in place in time.

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 in the thickly-jungled country two-thirds the size of the European Union.

DELAY?

Veteran opposition leader Tshisekedi said he could accept a delay but only if the head of the national election commission, who 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 denied he was a founding PPRD member.

Tshisekedi alleged the existence on paper of fake polling stations to allow vote-rigging, an allegation which authorities have denied. His party also accuses Kabila of using state media and transport assets in the service of his campaign.

For many Congolese, there was a last-minute scramble to find out where they should be voting on Monday. Gervis Ilunga, a 44-year-old security guard, said he registered in one Kinshasa voting 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 without securing an absolute 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.

(Writing and additional reporting by Mark John; Editing by Sophie Hares)