Italian carabinieri say the man was trapped and buried under six meters of earth for about eight hours on Thursday.

Dozens of firefighters worked around the tunnel before eventually freeing the man and pulling him to safety.

The trapped man -- from Rome -- was transferred to hospital while his suspected accomplices were also detained by the authorities.

"Two men from Naples were arrested for resisting a public officer and two others from Rome were arrested for the damage caused," the carabinieri press office said.

"The investigation is still underway, we do not exclude that they are thieves, this is one of the hypotheses," the statement added.

According to media reports, the four men are suspected of planning to rob a nearby bank on 15 August, when Italian shops close for the public holiday, Ferragosto.

The tunnel they were digging was found underneath an empty shop on a busy road near the Vatican City.

"No one had really paid attention because the shop had been rented out and everyone thought it was being renovated, and there was no noise," a local resident told AFP.