The second attack also happened on the Paraguay River when a 49-year-old man was found dead after being attacked by piranhas.

He had been reported missing hours earlier, and he was also found with severe bites to the face. In this case, however, it is believed the man died from a heart attack and only then was he attacked by the piranhas.

The Paraguay River is one of the biggest in the country, in the Ita Enramada neighbourhood, just south of the capital Asuncion.

Two other people were found dead with piranha bites on their bodies in the Tebicuary river on Sunday.

There have been further alleged attacks, which were not fatal but resulted in serious injuries, on the Parana River at the Bella Vista Fishing Club, which is in the department of Itapua.

The attacks follow on from other incidents reported in Argentina recently, including a teenage girl who had a toe bitten off.