The demonstrators had been seeking a higher minimum wage than the one approved this week by the government of Prime Minister Ariel Henry, when a passing police vehicle fired at them, according to a Reuters witness and a union leader present.

Lazzare Maxihen, who worked for Haitian media group Roi des Infos, was initially wounded and then died in the hospital on Wednesday, according to a hospital official who asked not to be identified.

Two other reporters were wounded in the shooting, according to Robest Dimanche of Haiti's union of online journalists, or CMEL, who was present at the demonstration.

The prime minister later condemned as "brutal acts" the journalist's death as well as the violence that caused injuries, pledging to protect peaceful demonstrations.

"The government reiterates the responsibility of public authorities to ensure order and security," Henry wrote in a post on Twitter.

Dominique St Eloi, a factory workers' union leader who was also present at the demonstration, said it had been calm when police began shooting from the vehicle.

It was not immediately evident why they fired. A spokesman for Haiti's National Police did not immediately reply to a request for comment.

Haiti on Monday raised the minimum wage by as much as 54 per cent following weeks of demonstrations by garment workers who say their wages are not enough to keep up with the rising cost of living.

Employees in the clothing manufacturing sector, which export finished products to US retailers, received a 37 per cent increase. That took their wages to just under $US7.50 ($A10.30) per day - half what union leaders had demanded.

Haiti is the poorest country in the Western Hemisphere.

Australian Associated Press