The US Geological Survey said the epicentre of the aftershock was located 9.8 miles (15.8 kilometres) north-northwest of Port-de-Paix, the city hard hit by Saturday night's 5.9 magnitude quake.
President Jovenel Moise went on Twitter to urge residents to "remain calm".
According to a statement from the country's Civil Protection agency, several people were injured in Port-de-Paix, Gros-Morne, Chansolme and Tortuga island, where houses were destroyed or damaged.
The USGS registered the quake some 19 km off Ti Port-de-Paix at a depth of 11.7 km.
In 2010, Haiti was hit by a catastrophic 7.0 magnitude quake that killed approximately 230,000 people.
Some of the injuries were sustained when people panicked after the quake, the civil protection agency said.
A powerful 5.9 natural disaster off the coast of Haiti has damaged some structures, according to the country's Civil Protection.
After shocks were reported in the Caribbean, including the Dominican Republic, Puerto Rico and the Virgin Islands.
In the town of Gros-Morne, one bed was covered in rubble, while the exterior walls of some homes were visibly cracked. On Sunday morning he said that he was en route to Port-de-Paix and Gros-Morne.
Moise tweeted pictures from Port-de-Paix, where he was briefed at the region's emergency response center, met victims, viewed damage to the police headquarters and offered thanks to local officers. Parts of a hospital and an auditorium collapsed in Gros-Morne, where parliamentarian Alcide Audne told The Associated Press that two of the deaths occurred.
Le Nouvelliste newspaper said one person died when an auditorium collapsed in the town of Gros Morne, and that detainees were released from a police holding cell that was damaged.
Impoverished Haiti, where many live in tenuous circumstances, is especially vulnerable to earthquakes.
Haitian officials said a convoy bringing food and drinking water was headed to the afflicted zone.
In 2010, a magnitude 7.1 tremor killed more than 250,000 people in Haiti.