The tremor hit the Campi Flegrei (Phlegraean Fields) area in southern Italy at 12:07 pm (10:07 GMT), at a depth of three kilometres, followed 15 minutes later by another of a 3.5 magnitude.

It was felt in Naples city centre and sent people into the streets in the surrounding areas, including in Pozzuoli, according to the ANSA news agency.

Two metro lines were suspended, according to RAI News, but there were no immediate reports of damage or injuries.

Seismic activity is nothing new in the area, which is Europe's largest active caldera -- the hollow left after a volcanic eruption.

It stretches from the outskirts of Naples into the sea, measuring some 12 by 15 kilometres (7.4 by 9.3 miles).

But many of the 500,000 inhabitants living in the danger zone have been spooked by larger than usual quakes in the past year.

A 4.4 magnitude quake on March 13 caused several light injuries and damage to some buildings, 10 months after another similar tremor in May 2024 -- which was the biggest for 40 years.

The volcanic eruption of Campi Flegrei 40,000 years ago was the most powerful in the Mediterranean.

A resurgence of seismic activity in the early 1980s led to a mass evacuation which reduced Pozzuoli to a ghost town.

Specialists, however, say a full-blown eruption in the near future remains unlikely.