At least 50 people died when a gas tanker exploded in the Haitian city of Cap-Haitien on Tuesday morning, according to the local deputy mayor.  

"I saw on the scene between 50 and 54 people burned alive," Deputy Mayor Patrick Almonor said. "It is impossible to identify them."

About 20 houses in the area also caught fire following the explosion, according to Almonor, raising fears of a heavier toll. 

"We don't have the ability to treat the number of seriously burned people," a nurse told AFP, worring that they won't be able to save them all.

Haitian Prime Minister Ariel Henry said the explosion left "around 40 people" dead and dozens injured, as he decreed a period of national mourning.

"I learned with sadness and emotion the terrible news of the explosion of a gas tanker last night in Cap-Haitien," he tweeted.

"Three days of national mourning will be decreed throughout the land, in memory of the victims of this tragedy which has devastated the whole Haitian nation," he said.

Ariel said field hospitals would be rapidly deployed to help care for the blast victims.

According to Almonor, it appeared the truck driver lost control as it swerved to avoid a motorcycle taxi and the tanker flipped over.

Almonor said fuel spilled onto the road and pedestrians rushed to collect the tanker's gas, which is currently in short supply as Haiti grapples with a severe fuel shortage caused by the tightening grip of criminal gangs on the capital Port-au-Prince.

The Caribbean nation has never produced enough electricity to meet the needs of the whole population. Even in well-off parts of the capital, the state-run Haiti electric utility only provides, at most, a few hours of power a day.

(With input from AFP)