“The bomb was found by fishermen on the bank of the River Po due to a decrease in water levels caused by drought,” Colonel Marco Nasi said.
About 3,000 people living nearby were evacuated for the disposal operation by the army.
The area's airspace was shut down, and navigation along that stretch of the waterway as well as traffic on a railway line and state road close by were halted.
Bomb disposal experts removed its detonator and took it 45 km away to be destroyed in a controlled explosion in a quarry.
The device was defused at Borgoforte, in the dried out Po bed near Mantua.
The Po Valley has been hit by the worst drought in 70 years and water levels are 80 per cent below their usual level at this time of the year.
Almost half the valley's crops are threatened as a result.
