Schools shut, more flights scheduled as quakes constantly shake Santorini

ATHENS (Reuters) - Schools remained shut and additional flights were scheduled to help people leave the Greek island of Santorini on Monday as dozens of tremors shook the popular holiday destination for a fourth day.

Tremors have been recorded between the volcanic islands of Santorini and Amorgos in the Aegean Sea since Friday, forcing authorities to close schools in Santorini and the nearby islands of Ios, Amorgos and Anafi.

Quakes, some with a magnitude above 4, rattled Santorini every few minutes on Monday as people were advised to stay out of indoor spaces and small ports. Disaster response units were deployed on the ground as a precaution.

Experts have said that the seismic activity on the island, some of whose most populated areas are perched on steep cliffs, will continue for weeks.

"We estimate it (the activity) will continue for some days and there could be a lengthy seismic sequence," Efthymios Lekkas, a professor of tectonic geology and disaster management, and part of a team of experts assessing the situation on the ground, told Greek television.

Local officials said that permanent residents were not particularly worried as they have been used to quakes but some who were on the island for work were moving out.

Aegean Airlines said it would operate three additional flights to and from Santorini on Monday and Tuesday to facilitate the travel of residents and visitors upon a request by Greece's Civil Protection Ministry.

Greece sits on multiple fault lines and is often rattled by earthquakes.

One of the largest volcanic eruptions in history, around 1600 BC, formed Santorini in its current shape. The last eruption in the area occurred in 1950.

Experts said a mild volcanic activity also recorded near Santorini in recent days was not linked to the quakes.

(Reporting by Angeliki Koutantou; Additional reporting by Karolina Tagaris and Antonis Pothitos; Editing by Angus MacSwan)