Sao Jorge, one of the nine major Azorean islands, has been hit by around 14,000 minor quakes over the past week, Reuters reports, peaking at magnitude 3.3 so far.

Military support has been sent to Sao Jorge and an evacuation plan drawn up to ensure islanders can get to safety; around 8,000 people are thought to live on Sao Jorge, although about 1,500 are understood to have already left the island.

The CIVICA seismic surveillance centre raised its volcanic alert to level four last week, with five being the highest possible level. The island’s main volcanic fissure last erupted in 1808, although the island has been hit by significant earthquakes since then.

The Foreign Office updated its advice for Portugal and the Azores at the weekend, highlighting the reports of increased seismic activity on Sao Jorge since 19 March.

Travellers are advised not to travel to the island except for essential purposes after local authorities activated their earthquake prevention plan.

"The areas of flat terrain, known locally as fajas, at the foot of the cliffs overlooking the sea in the Velas municipality, are being evacuated due to the possibility of landslides following a yellow weather warning that is predicting heavy rain and high winds," said the FCDO.