The refugees fought Zairean soldiers, who restored order at the Chimanga camp after about an hour, but worried UN refugee officials were rushing their chief security adviser to the camp.
'It was a very serious security incident, and we are afraid that the rioting may spread to other areas,' Capt. Declan O'Brien, a member of the Irish army contingent in Zaire, told The Associated Press.
Chimanga, 50 miles (80 kms) from Bukavu in eastern Zaire, is home to 15,000 Hutu refugees.
About 1.2 million Hutus fled Rwanda for eastern Zaire after Tutsi-led rebels fought their way to power in July. The refugees include leaders of the deposed Hutu-led government and other who fear revenge killings for massacres of up to 500,000 Tutsi civilians during the fighting.
O'Brien said 20 people were wounded when someone lobbed a grenade at the marketplace, which is adjacent to the camp.
No deaths or injuries were reported in the riot. Lyndall Sachs, a spokeswoman for the UN High Commissioner for Refugees, said she had no other details.
The riot reflects a growing militancy among the refugees, which would be a serious security concern, said Ms. Sachs.
'Such incidents indeed make us worry a lot, as they are a perfect recipe for starting a chain of security incidents,' she said.
Meanwhile, UN officials reported that Hutus who have returned to their homes in Rwanda are coming back to the camps in Zaire.
At least 470 Hutu refugees came back to Zaire in the past four days, Sachs said. She said they were harassed in Rwanda, but did not give details of why they returned to Zaire.
In the past month, an estimated 45,000 Hutu refugees have gone back to Rwanda, most of them women, children and old men.Reuse content