The police chief for the northwest region, Jackson Hilaire, said at least seven people were killed and more than 100 injured in Port-de-Paix.
A magnitude 5.2 aftershock struck Haiti on Sunday, even as survivors of the previous day's temblor were sifting through the rubble of their cinderblock homes. Authorities said at least 12 people died and 188 were injured.
Homes and a hospital were also reported to have been destroyed by the quake.
The quake was one of the strongest in Haiti since 2010 when a magnitude 7 left about 300-thousand people dead.
At least five deaths were in the the Port-de-Paix area, Jerry Chandler, the head of the country's Civil Protection disaster response unit, told the Miami Herald.
Haitian Prime Minister Jean Henry Ceant took to Twitter to urge people to remain calm following the quake and provide details on the emergency response.
Rescue workers in Haiti said they were not looking for any more victims, but evidence of the quake's destruction was on view.
Poverty and political instability have prevented Haiti from shoring up weaker buildings despite the two major fault lines along the island of Hispaniola, which it shares with the Dominican Republic.
Meanwhile, dozens of people could be seen through debris before hauling away rebar to recycle and sell.
Some of the injuries were sustained when people panicked after the initial quake, the civil protection agency said.
The agency said Port-de-Paix, Gros-Morne, the town of Chansolme and the island of Tortuga suffered some of the worst damage and some houses were destroyed.
The prison and police station in Port-de-Paix were damaged, leading some inmates to try to escape. He also said the government had sent water and food.
A major global relief effort followed the devastating 7.0-magnitude quake that struck the island in January 2010, leaving more than 1.5 million people homeless.