Twenty people were killed in a major accident on a highway south of Haiti's capital, hospital officials said.

"We have counted 20 dead at the Notre-Dame de Petit-Goave hospital," hospital administrator Joel Charles told AFP by phone on Saturday.

"Seventeen of the bodies were brought to the morgue and three died after being rushed for treatment by Haitian Red Cross ambulances," he explained.

About 40 people were injured in the crash between the capital and the town of Petit-Goave.

"Some of the injuries are critical, a lot of head trauma and broken bones. We need surgeons," Charles said.

"The city's capacities are overwhelmed by this accident, and we need medical staff," a local radio reporter pleaded on air.

The impoverished Caribbean nation's infrastructure is in generally disastrous shape after the catastrophic 2010 earthquake, which killed some 250,000 people, and left roads and buildings in and around the capital in ruins.