The strongest earthquake recorded was magnitude 4.6 at 3:55 p.m. Sunday, at a depth of 14 kilometers (9 miles), the Athens Geodynamic Institute said.

Greek authorities have warned of an increase in seismic activity around the Aegean tourist island of Santorini, advising people to avoid four ports, empty their pools, refrain from gathering in indoor spaces and shut schools on Monday.

Greece's tourist island of Santorini on Sunday braced for the prospect of more tremors after more than 200 small earthquakes shook the site of one of the largest volcanic eruptions in recorded history,