0250 GMT July 21, 2019
The country is on edge ahead of the December 23 vote to replace President Joseph Kabila, who has ruled the resource-rich nation since 2001.
Unrest erupted in Tshikapa, a city in the restive central Kasai region, on Sunday when the planes of two rival candidates -- opposition heavyweight Felix Tshisekedi and former education minister Maker Mwangu -- landed at the airport just a few hours apart.
Sources with observers at the scene said at least one person had been killed and around 20 arrested, Presstv Reported.
But others in the region said the toll could be higher.
"A young local chief who was among Maker Mwangu's supporters was attacked with stones," Faustin Dostin Luange of the local community radio station told AFP.
The man was rushed to hospital but later died of his injuries, he said.
The attack prompted a furious reaction from other Mwangu supporters, who then attacked a motorcycle driver "whom they took for an activist of (Tshisekedi's) party and beat him to death", he said.
"I have seen two bodies but the toll could rise." Other sources also spoke of two dead, and although the police confirmed the unrest, they did not give a toll.
Authorities are on alert for a resurgence of communal conflict in the wider Kasai region, which descended into violence in summer 2016 after troops shot dead the Kamwina Nsapu, a local tribal chief from the Luba ethnic group who opposed Kinshasa.
Rebels fighting in his name have since battled Congolese troops as well as a pro-government militia called the Bana Mura.
Around 3,000 people were killed in less than a year of unrest.