The death toll in Haiti following a powerful 7.2 magnitude earthquake has jumped to 724, the country's civil protection agency has said.
An additional 2,800 people were injured in the tremor that struck yesterday.
Haitians laboured overnight to pick through shattered buildings in search of friends and relatives trapped in the rubble after the devastating earthquake struck.
The quake flattened hundreds of homes in the impoverished country, which is still clawing its way back from another major quake 11 years ago, and has been without a head of state since the assassination of its president last month.
Southwestern Haiti bore the brunt of the blow, especially in the region in and around the city of Les Cayes. By yesterday evening, Haitian officials had registered nearly 2,000 people injured.
Churches, hotels, hospitals and schools were badly damaged or destroyed, while the walls of a prison were rent open by the violent shudders that convulsed Haiti.
"We need to show a lot of solidarity with the emergency," said Haiti's Prime Minister Ariel Henry, a neurosurgeon who was thrust to the forefront of the troubled country after the assassination of President Jovenel Moise on 7 July.
Some Haitians said they would spend Saturday night sleeping in the open, traumatized by memories of the magnitude 7.0 quake in 2010 that struck far closer to the sprawling capital, Port-au-Prince, and killed tens of thousands of people.
Footage of the aftermath posted on social media showed residents reaching into narrow openings in piles of fallen masonry to pull shocked and distraught people from the debris of walls and roofs that had crumbled around them.
Access to the worst-hit areas was complicated by a deterioration in law and order that has left key access roads in parts of Haiti in the hands of gangs, although unconfirmed reports on social media suggested they would let aid pass.
Following Moise's assassination, which authorities have alleged was carried out by a group of largely Colombian mercenaries and Haitian accomplices, Prime Minister Henry said officials would aim to hold elections for a new president as soon as possible.
However, reports earlier this week suggested that the vote initially earmarked for September would not take place until November. The chaos unleashed by Saturday's disaster is likely to make the task of holding prompt elections harder still.
The quake sent tremors traveling as far as Jamaica and Cuba. Countries in the region quickly offered help to Haiti.
"I am saddened by the devastating earthquake that occurred in Saint-Louis du Sud, Haiti this morning. Through USAID, we are supporting efforts to assess the damage and assist efforts to recover and rebuild," said US President Joe Biden.
A medical brigade of 253 Cuban doctors deployed in Haiti was traveling to treat the injured and adapt a Port-au-Prince hospital until now used for Covid-19 patients, their head said on Cuban television.
In Ecuador, Quito Fire Department said it was preparing to send a team of 34 personnel specialised in urban search and rescue. Mexico, Chile, Argentina, Peru and Venezuela also offered help while Spanish Prime Minister Pedro Sanchez said Haitians "can count on the support of Spain to come through this terrible event."
Tennis star Naomi Osaka, whose father is Haitian, said she was going to donate her prize money from an upcoming tournament to help quake victims.
The damage in the city of Les Cayes appeared to be significant, including the collapse of a multi-story hotel.
Mr Henry, who surveyed the damage via helicopter, declared a state of emergency for one month while calling on the nation to "show solidarity" and not panic.
Shortly after the quake, the US Geological Survey issued a tsunami alert, but lifted the warning soon after.
A 7.0-magnitude quake in January 2010 left much of Port-au-Prince and nearby cities in ruins, killing more than 200,000 and injuring some 300,000 others.
More than 1.5 million Haitians were made homeless, leaving island authorities and the international humanitarian community with a colossal challenge.
Besides hundreds of thousands of homes, the quake also destroyed administrative buildings and schools, not to mention 60% of Haiti's health care system.
The rebuilding of the country's main hospital remains incomplete, and non-governmental organisations have struggled to make up for the state's many deficiencies.