Those injured in the attack Wednesday by the ferocious fish included a girl who lost part of a finger, Health Undersecretary Gabriela Quintanilla told reporters.

Quintanilla said the attack occurred Wednesday off the coast of Rosario, some 310 kilometers (200 miles) north of Buenos Aires.

A medical official, Gustavo Centurion, said the attack which began at mid-morning on Christmas Day was "very aggressive."

"There were some people that the fish literally had torn bits of flesh from," he said.

The region has been hit by a heat wave with temperatures soaring to some 38 degrees Celsius (more than 100 degrees Fahrenheit) prompting thousands to seek relief in the waters of the Parana River, which is packed with carnivorous fish.

Officials said the unusually warm weather also was apparently responsible for the fish congregating on the river's surface before the attack.