A fierce storm has killed at least 14 people in northern Argentina and southern Brazil, BBC reported.
Dozens more were injured as rain, hail and winds of over 100km/h (60 mph) destroyed their homes.
At least 10 people were killed and more than 50 hurt in Argentina, according to local officials.
In Brazil four people died in the city of Guaraciaba, and there were unconfirmed reports of two more deaths in Sao Paulo.
The storm also damaged homes in Paraguay.
Several local media reports described the storm as a tornado, but meteorologists called it a severe depression, where tropical warm air and frigid air collide to create instability.
'Incredible' devastation
The worst affected places in Argentina were the small towns of Santa Rosa, Tobuna and Pozo Azul, according to Ricardo Veselka, the civil defence director for the town of San Pedro.
San Pedro mayor Orlando Wolfart described the devastation as "incredible".
"This is something we've never seen," he told reporters.
Argentina's Health Minister, Juan Manzur, is to travel to the region.
In Brazil extremely heavy rain caused traffic problems in Sao Paulo and cut off phone services in some neighbourhoods.
In Paraguay there were reports that 700 rural properties, as well as crops, had been damaged.
The temperature in the capital Asuncion fell from 35C to 12C.