A 49-year-old builder was killed by a rocket flying into his face and a 51-year-old restaurant owner died when a firecracker went off near his head as he was trying out a firework battery just before midnight, local police said.

Both accidents occurred in the Campania region in southern Italy, where powerful illegal fireworks are widely available and popular among residents.

A car apparently packed with illegal fireworks exploded in Naples on New Year's Eve, severely injuring the two teenagers inside, the police said.

Dozens more were injured overnight in and around Naples, the capital of Campania, including a six-year-old girl and a five-year-old boy who were hospitalised with burns caused by explosions but were later released.

There were several injuries in other parts of Italy too, with an 11-year-old Roma boy in Milan losing three fingers when an unexploded firecracker went off in his hand and one man losing the use of his hand due to a blast near Foggia.

The biggest New Year parties were in Rome, where 300,000 packed the avenue leading to the Colosseum for a concert, and Venice, where 70,000 crowded into St Mark's Square dressed in white costumes and masks for an "All White" party.