Landslides have killed at least 154 people in south-west Colombia and left many more injured, says President Juan Manuel Santos.
Hours of heavy rains overnight caused rivers to burst their banks, flooding homes with mud in Putumayo province.
An unknown number of people are missing. One army officer said the main local hospital was struggling to cope.
Mr Santos, who has travelled to the area, said troops had been deployed as part of a national emergency response.
He declared a state of emergency in the region.
The national fire service said at least 190 people had been injured.
The region’s governor, Sorrel Aroca, told Colombian media that whole neighbourhoods had been buried.
Rescue services said their efforts had been hampered by continuing bad weather and damaged infrastructure.
“There are mobility issues on almost 80% of the roads, and from where the road ends, it is three hours to where the landslide took place,” said one police officer.
Bridges have also been swept away.
Jose Antonio Castro, mayor of the provincial capital Mocoa, told Caracol radio that the town was “totally isolated”, without electricity and water.
On arriving at the scene, President Santos told reporters, “My heart and the hearts of all Colombians are with the victims of this tragedy.”
An alarm had sounded as the river’s levels rose, leading many people to leave their homes for shelter, and avoiding wider loss of life, Colombia’s El Tiempo newspaper said.