While rescue teams toiled to dig out survivors of Saturday's 7.2 magnitude quake, a storm dumped heavy rain on the southern coast of Haiti on Monday, bringing flooding near the worst-hit areas and exacerbating the humanitarian crisis, residents said.

Deus Deronneth, a politician from the Jacmel region, posted a video on Twitter showing a torrent of water sweeping through a local town and confirmed the flooding to Reuters.

The earthquake brought down tens of thousands of buildings in the deeply impoverished country, which is still recovering from a major tremor years ago and the assassination of its president, Jovenel Moise, on July 7.

Dozens of churches, hotels, homes and schools were seriously damaged or ruined by the quake. Haitian authorities said on Monday afternoon that 1419 fatalities had been confirmed, with 6900 people injured and 37,312 houses destroyed.

Data circulating among aid groups indicated over 450 additional deaths had been logged in the hardest-hit department, and Haitian officials warned the toll was likely to rise.

The areas in and around the city of Les Cayes - about 150 kilometres west of the Caribbean country's capital Port-au-Prince - suffered the most damage, putting enormous strain on local hospitals, some of which were badly damaged.

Collapsed buildings lined the main street of the seafront city of 100,000 people. Dozens of men dug through rubble from a hotel whose owner died in the quake, residents said.

The city's general hospital was overwhelmed, with doctors and nurses attending patients in tents in its crowded parking lot because there was no more room inside.

Prime Minister Ariel Henry said there was no time to lose.

"From this Monday, we will move faster. Aid provision is going to be accelerated," he wrote on Twitter. "We will multiply efforts tenfold to reach as many victims as possible with aid."

As well as damage to some roads in the area, access to Les Cayes has been complicated by months of political turmoil in Haiti, which has left gangs in control of key access routes to parts of the country.

The United Nations called for a "humanitarian corridor" to enable aid to pass through gang-held territories.

It was unclear whether presidential elections planned for November to draw a line under the political confusion since Moise was assassinated could be held.

Aid workers were hurrying to beat the onset of Tropical Depression Grace, which on Monday evening was moving west-northwest along southern Haiti, dumping heavy rain.

The US National Hurricane Center said Grace could douse some areas with up to 38 centimetres of rain through Tuesday.

Many Haitians remain traumatised by memories of a magnitude 7.0 quake that struck far closer to Port-au-Prince, killing more than 200,000 people.

Australian Associated Press