National police on Tuesday said they were conducting operations in several parts of Artibonite.
Residents of Jean-Denis counted 70 bodies on Sunday morning after an attack by the Gran Grif gang, the National Network for the Defence of Human Rights (RNDDH) said in a report, matching the estimates of the Defence Plus rights group but far above official estimates, which put the death toll at around 16.
RNDDH said some 30 more people were wounded, and victims included infants, pregnant women, teenagers and an 80-year-old man.
Armed men withdrew from Jean-Denis on Monday, RNDDH said, but on Tuesday they repositioned themselves in nearby Pont Benoit and were attempting to launch another offensive in the town of Marchand Dessalines, some 20km north.
Videos shared on social media showed armed men reportedly belonging to the Kokorat San Ras gang, a close ally of the powerful Gran Grif, distributing cash to residents in Marchand Dessalines.
Gran Grif has been designated a terrorist organisation by the United States and neighbouring Dominican Republic.
Residents told Reuters local self-defence brigades did not have the firepower to hold off the gangs, which would wait during the day when police were present but begin shooting and setting fire to buildings at night.
RNDDH, whose report followed interviews with local authorities, police and residents, said Gran Grif's attack on Jean-Denis followed weeks of threats and residents did not flee because they believed the self-defence brigade would protect them.