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.

ATHENS (Reuters) -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.

More than 200 tremors have been registered since Friday between the Greek volcanic islands of Santorini and Amorgos.

Greece sits on multiple fault lines and is often rattled by earthquakes. Santorini is visited by about three million people annually, including many British tourists. One of the largest volcanic eruptions in history, around 1600 BC, formed the island in its current shape, while the last eruption in the area occurred in 1950.

Greek authorities have advised people on the Aegean island of Santorini to shut schools on Monday, avoid two small ports and refrain from gathering in indoor spaces after increased seismic activity in the area over recent days.

Greek officials are warning those on the popular tourist island destination of Santorini to stay alert in the coming days due to increasing seismic activity which could mean a strong earthquake is possible.

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,