The governor of Democratic Republic of Congo's capital Kinshasa on Wednesday ordered a halt to campaigning in the city for Sunday's presidential election for security reasons.

"The information in our possession attests that in all the political camps of the main presidential candidates, extremists have prepared and are preparing for a street confrontation in the city of Kinshasa during election campaign activities," Kinshasa Governor Andre Kimbuta said in a statement.

More than 100 people have died in clashes between rival ethnic groups in the northwestern region of the country this week, local activists said.

The fighting in Mai-Ndombe province is some of the worst to hit the normally peaceful area in years and comes days before Sunday's long-delayed presidential, legislative and provincial elections, which many fear could turn violent.

The fighting between the Batende and Banunu ethnic groups broke out on Sunday over the disputed location of a Banunu chief's burial, said Jules Bango, an activist in the town of Yumbi, on the banks of the Congo River.

"Today we have identified almost 120 deaths, and there are 71 others wounded in the hospital," Bango told Reuters.

Many people had fled across the river into neighbouring Congo Republic, he added.

Another local activist, speaking on condition of anonymity, said the death toll could rise as high as 150.

He said the upcoming elections, in which Batende leaders are supporting the ruling coalition and Banunu leaders are backing opposition candidates, have raised tensions between the two groups.

Mai-Ndobe's governor did not respond immediately to requests for comment.