Rescue workers are rushing to locate survivors of the deadly earthquake that struck Haiti on Saturday as a tropical storm is heading towards the Caribbean nation.

At least 1,297 people are known to have died in the 7.2-magnitude quake and an unknown number are still missing.

Tropical Depression Grace is expected to pass over the worst affected area later on Monday.

It is feared heavy rain brought by Grace could trigger landslides.

Roads already made impassable by the quake could be further damaged by the rains, so aid teams are racing to get essential provisions to the quake-hit region before Grace hits.

A tropical storm watch is in effect for the entire coast of Haiti as well as for the neighbouring Dominican Republic.

Search and rescue teams have been arriving from the United States and Chile, with more on the way from Mexico. Cuban medical teams are already in Haiti and helping people.

Humanitarian organisations say survivors need drinking water and shelter. More than 30,000 families have reportedly been left homeless.

Homes, churches and schools were among buildings flattened in the quake. Some hospitals were left overwhelmed and in need of supplies as they struggled to treat the injured, of whom there are an estimated 5,700.

The earthquake compounds problems facing the impoverished nation, which is already reeling from a political crisis following the assassination of its president last month.

The south-west of Haiti appears to have suffered the worst of the damage, especially around the city of Les Cayes.

Footage on social media showed residents desperately trying to pull victims from ruined buildings.

"The streets are filled with screaming," Archdeacon Abiade Lozama, head of an Anglican church in Les Cayes, told the New York Times. "People are searching, for loved ones or resources, medical help, water."

The epicentre of Saturday's quake was about 12km (7.5 miles) from the town of Saint-Louis du Sud, the US Geological Survey (USGS) said.

But the tremor could be felt in the densely-populated capital of Port-au-Prince, some 125km away, and in neighbouring countries.

Prime Minister Ariel Henry declared a month-long state of emergency and urged the population to "show solidarity".

The Pope offered prayers for the victims during a Sunday address and expressed hope that aid would arrive soon.

Japanese tennis star Naomi Osaka, whose father is from Haiti, said she would donate her earnings from next week's Western & Southern Open to help finance relief efforts.

Aftershocks were felt after the initial tremor on Saturday, with the USGS initially warning the earthquake could result in thousands of fatalities and injuries.

A 2010 earthquake in Haiti killed more than 200,000 people and caused extensive damage to the country's infrastructure and economy.