ROME - An Italian man threw his 16-month-old son off a bridge into the river in Rome in a fit of rage following a row with his partner over custody, Italian media reported.

The man, 26, admitted to police that he had thrown his son into the freezing waters of the Tevere river after arguing with the infant's mother.

He was caught in the act by a passing prison officer, who said the father was overwrought and yelled out before throwing the child over the edge.

The man, who is unemployed and has a criminal record for drug dealing, tried to flee the scene but was detained shortly afterwards by police, reports said.

Divers from the fire brigade searched the river for the child, but their efforts were hampered by strong currents and poor weather conditions.

"It is an appalling story, which causes anguish and astonishment. It was an act of extreme cruelty," said the deputy mayor of Rome, Sveva Belvisio.

"Our thoughts go to the innocent child - a victim of the violence of a father who, instead of defending and protecting him, treated him as an object on which to vent his frustration," she said.

Belvisio called for an "immediate and exemplary sentence" for the father.