Campi Flegrei schools closed on Tuesday amid seismic storm.

The Campi Flegrei or Phlegraean Fields, a highly seismic area in Italy's southern Campania region near Naples, was shaken by a 4.4 magnitude earthquake on Monday evening.

The earthquake was part of an ongoing "seismic storm" of tremors, with the epicentre near the town of Pozzuoli, according to Italy’s National Institute of Geophysics and Volcanology (INGV).

The earthquake, which occurred at 20.10 at a depth of three kilometres, was the strongest to hit the Campi Flegrei area in the past 40 years.

[DATI #RIVISTI] #terremoto Md 4.4 ore 20:10 IT del 20-05-2024 a Campi Flegrei Prof= 2.6 Km #INGV_38759141 https://t.co/qqSmIFurdb

— INGVterremoti (@INGVterremoti) May 20, 2024

The quake resulted in mild structural damage in Pozzuoli, firefighters said, and sent people running into the streets in panic, with many of them spending the night in their cars.

There were around 150 tremors registered over five hours on Tuesday evening, the INGV said, including a 3.5 magnitude earthquake at 19.59 and a 3.9 magnitude earthquake at 21.46.

Schools in areas around Pozzuoli, Bacoli, Quarto and Monte di Procida as well as some parts of Naples will be closed on Tuesday as a precautionary measure, local authorities said.

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Declared a regional park 20 years ago, the Phlegraean Fields area is a highly seismic zone of supervolcanic calderas, situated to the west of Naples and about 50 kilometres from Mount Vesuvius.

The Campo Flegrei volcano last erupted in 1538 however earthquakes have been common in the area since 1950, with a surge of seismic unrest in the early 1980s.

Experts believe the recent spike in seismic activity is linked to bradyseism, a phenomenon that involves the gradual uplift or descent of part of the earth's surface, caused by the filling or emptying of underground magma chambers or hydrothermal activity.

There are 15 towns in the Campi Felgrei area with a combined population of more than half a million people living in the so-called 'red zone' most at risk.

Earlier this year the Italian government announced new measures in light of the increased seismic activity in the area, updating emergency plans for a possible mass evacuation.