The Venezuelan government declared a state of emergency yesterday, as torrential rains swept families, homes, bridges and highways away, leaving an estimated 2,000 people feared dead.
The centre of Caracas looked like it had been struck by an earthquake as wrecked cars lay abandoned on the city streets and church pews were filled with refugees, who had lost homes and possessions.
A Catholic priest conducted a national pray-in on television, while citizens turned up at donation centres with food, nappies and medicines.
"God have mercy on the Venezuelan people," said President Hugo Chavez, who faced the stiffest test yet of his presidential rule.
Rescuers searched for survivors as officials feared the death toll could reach catastrophic proportions.
The governor of Caracas, Mr Hernan Gruber, said 80 people had died in the capital alone, and a senior police official said that figure would probably reach into the hundreds.
In the hills that surround Caracas, emergency teams searched through tonnes of mud and rocks which engulfed entire slums. Rescuers told radio and television stations that 2,000 people may be trapped under the mudslides.
As the sun broke through clouds for the first time in days, military helicopters flew rescue missions after reports that hundreds of people were perched on rooftops to escape rising flood waters. In one seaside building near Caracas, 500 people were waiting to be rescued.
In a slum near the capital, 20 street children were trapped in a school where they had sought refuge, according to Father Juan Carlos Corriales.
The Defence Minister, Mr Raul Salazar, said naval ships joined rescue and relief operations along the Caribbean coast. On Thursday helicopter crews braved fog and driving rain to pluck 1,300 people from the roofs of their flooded houses.
As chaos continued in the capital, police said they had arrested several looters.
A few blocks from Caracas city centre, residents cleared massive amounts of mud and water from their homes and retrieved whatever belongings were not carried away by the torrent.
Foreign aid started flowing in or was about to arrive from European and Latin-American countries, Japan, China and the US, said the Foreign Minister, Mr Jose Vicente Rangel.
President Chavez said the tragedy forced 43,000 people to abandon their homes, or what was left of them. But he said many people refused to evacuate, apparently for fear of looting. "I appeal to your good sense. Let's leave," he said.
The rains had started about two weeks ago, but most of the devastation came after they intensified on Wednesday night.