The Angop news agency said flood-waters from the Capitao river, swollen by nearly 24 hours of torrential rain in the area, washed through the market, where many young Angolans congregated to wash cars and bicycles, Reuters reported.
More than 30 people were believed to be missing.
As with much of southern Africa, southern Angola has been suffering one of its worst droughts in memory caused by a strong El Nino weather pattern in the Pacific Ocean.