According to the US Geological Survey, the magnitude 4.9 quake occurred just after 5:00 am (09:00 GMT) around 5.5 miles (9 kilometers) off the coast of the isolated Grand'Anse department, some 185 miles west of Port-au-Prince, AFP reported.
The Haitian Red Cross said emergency workers were looking for people who may still be trapped under the ruins.
"Efforts continue to find survivors," the group said.
The majority of victims lived in the poor neighborhood of Sainte Helene, in the town of Jeremie.
In 2010 a massive 7.0 quake killed more than 200,000 people in Haiti, turning the capital Port-au-Prince into ruins and making 1.5 million people homeless.
In August 2021 the southwest peninsula was ravaged by an even stronger, 7.2 magnitude quake that killed more than 2,200 people and destroyed 130,000 homes.
AMK/PR