At least 70 people were killed in Haiti's breadbasket Artibonite region, the director of a human rights group said on Monday, a significantly higher toll than initial government figures.
A police report said at least 16 people were killed and 10 others injured on Sunday amid a conflict with the Gran Grif gang.
Local media said the violence began in the Jean-Denis neighborhood.
UN: More than 2,000 displaced
The attack follows United Nations reports that more than 2,000 people were recently displaced by armed raids in nearby Verrettes, prompting residents in Petite-Riviere to flee their homes.
The Artibonite department, a key agricultural area, has seen some of the country's worst violence as gang conflict spreads beyond the capital, Port-au-Prince.