Thousands of earthquakes, mainly of a low magnitude, have been recorded between Santorini and Amorgos, islands in the Cyclades group southeast of the Greek mainland. They have yet to cause either casualties or significant damage but have worried authorities and residents.

"Seismic activity in the maritime region between Thira (Santorini) and Amorgos is decreasing," the ministry of civil protection said in a press release late Saturday following a meeting with the national commission of seismologists.

The ministry attributed the activity to a combination of tectonic movement and deep magmatic activity.

The region has not experienced a phenomenon of such magnitude since records began in 1964, experts say.

Located where the African and Anatolian tectonic plates converge, the Aegean Sea is often hit by earthquakes.

Known for its spectacular volcanic caldera, a large depression that forms when a volcano erupts and collapses, Santorini is also part of a volcanic arc with two underwater volcanoes near to its coast, Nea Kameni and Kolumbo, which last erupted in 1950 and 1650 respectively.

Authorities put the level of seismic activity inside the caldera as similar to recent days, noting a decrease in the rate of local ground deformation.

The ministry aid preventative measures would remain in force, urging residents to be alert to the risk of landslides.

Schools will meantime remain closed until Friday on Santorini and the nearby islands of Ios, Anafi and Amorgos while a ministerial assessment meeting will be held Thursday.

Authorities declared a state of emergency in Santorini and Amorgos at the start of February for a month, with schools closing while a majority of Santorini residents elected to leave the island, which saw 3.4 million visitors in 2023, leading to complaints of over-tourism.

Prime Minister Kyriakos Mitsotakis recently announced a support package for local businesses and workers on the island, one of Greece's most popular tourism destinations.