Some 200 minor earthquakes were recorded in the sea and surrounding islands in just 48 hours, with the strongest, of magnitude 4.6, striking the waters between Santorini and Amorgos on Sunday afternoon.

The spate prompted Greece's civil protection late on Saturday to order schools closed down into Monday, while tents sprang up to house rescue teams sent to the island in response.

Authorities and experts said the tremors were triggered by tectonic rather than volcanic activity -- dampening fears of a destructive eruption.

But with the surrounding seas home to several significant fault lines in the Earth's crust, the possibility of a stronger earthquake to come could not be ruled out, said Kostas Papazachos, Professor of Geophysics at Thessaloniki Aristotle University.

"That is why there are some precautionary measures in place, precisely to limit the impact of a stronger earthquake," Papazachos told ERTNews on Sunday morning.

"When you have a sequence next to you that is so vivid, so intense, you have to be a bit careful, precisely because there is always the risk of that happening."

Greek authorities called for citizens to avoid large gatherings in enclosed spaces and stay away from certain ports of Santorini, derelict buildings and empty swimming pools of their water.

In case of a strong tremor, all citizens are called to get to high ground as far inland as possible.

The same measures are likewise in place for the neighbouring small islands like Amorgos.

Greece's fire service in the southern Aegean Sea region was on general alert, while a rescue service team with a search dog, helicopter, drones was already at the scene.

An emergency meeting was scheduled for Sunday afternoon chaired by Prime Minister Kyriakos Mitsotakis.

Santorini is one of the most popular Greek islands with tourists. It has a population of just 15,500 but welcomed 3.4 million visitors in 2023, raising concerns over overtourism.