Thousands of people were leaving the Greek island of Santorini by sea and air for a third day on Tuesday, as an unprecedented series of earthquakes shook the top travel destination.

Some 6,000 people have already left the island, known for its spectacular cliffside views and a dormant volcano, which has been hit by hundreds of tremors since last week, officials said.

A quake with a magnitude of 4.9 hit early on Tuesday morning amid other smaller tremors. No injuries or damage were reported on Santorini and the neighbouring islands of Anafi, Ios and Amorgos, which have also been affected by the seismic activity.

Experts say the region has not experienced seismic activity on this scale in recent history and do not know how long it will last.

"This is the first time this is happening, we have not seen it before," Athanassios Ganas, research director at the National Observatory's Institute of Geodynamics, told state TV ERT.

He noted that the area had been hit with over 40 earthquakes with a magnitude of over 4.0 in the past 72 hours.

Santorini lies atop a volcano which last erupted in 1950 — but an experts' committee on Monday said the current phenomenon was "not linked to volcanic activity."

According to the Greek coastguard, over 4,600 people have left the island by ferry since Sunday alone. 

The country's leading air carrier Aegean Airlines said it had flown nearly 1,300 people out of Santorini on Monday, with another eight flights able to carry 1,400 passengers scheduled for Tuesday.

Ferry services to Santorini have also been increased.

Schools on all four islands have been shut as a precaution until Friday, prompting many locals with children to leave until the situation stabilises.

Some tourists currently on the island say they are not overly concerned.

"I'm not so worried about the earthquake or volcano because I came from Tokyo," said Water Saito, a 43-year-old economist who spent a day on the island. 

He noted that the tremor levels in Santorini are negligible compared to the earthquakes experienced in Japan.

'Tiny' tremors

Roger Beauchamp from Arizona called the tremors "tiny."

"We've been feeling them all day, little light ones. So we're not afraid of them," he told AFP.

The head of Greece's earthquake planning and protection authority, Efthymios Lekkas, has said that an earthquake of 6.0 magnitude was unlikely.

"The residents of Santorini should feel safe. There must not be panic," he told Mega TV on Tuesday.

Greek Prime Minister Kyriakos Mitsotakis on Monday also appealed for calm, whilst admitting that the phenomenon is "very intense."

Santorini attracted about 3.4 million visitors in 2023.

European travel agents contacted by AFP said foreign visitors to Santorini at this time of year were minimal, with bookings expected in the spring.

Ted Stathis, who runs a local catamaran company and a sushi restaurant, said he expected the disruption to "blow over soon."

"I have to admit, it's something out of the ordinary," the 54-year-old said.

"I mean, we have had tremors throughout the years, but sporadically. These are just many, many concentrated."

"As long as they start subsiding, we should be in the clear," Stathis said, noting that most of his reservations start later this month.