A 55-year-old American has been found dead on the Greek island of Mathraki, the police said on Monday, the third tourist death in a week following a period of unusually hot weather.

Temperatures soared above 40 degrees Celsius (104 Fahrenheit) earlier this month, just as the holiday season began across Greece's remote beaches, ancient sites, and mountain trails.

The early heatwave has coincided with a spate of disappearances and deaths of tourists across the Mediterranean country, highlighting the dangers of heat exposure.

"There is a common pattern - they all went for a hike amid high temperatures," Petros Vassilakis, the police spokesman for the Southern Aegean, told Reuters.

The body of British TV presenter Michael Mosley was found on the island of Symi on June 9, following a four-day search operation by aircraft, drones, and boats. He had taken a walk alone in high temperatures before he disappeared.

Police did not share the identity of the dead American, whose body was found near a beach on Mathraki on Sunday. He was transferred to the island of Corfu where an autopsy will be carried out, a police official told Reuters.

A 74-year-old Dutch tourist was found dead on the island of Samos on Saturday and two hikers were found dead on Crete on June 5.

Rescue teams were also searching for two French women, aged 73 and 64, on the island of Sikinos, and a 59-year-old US policeman on Amorgos.

"There are two search operations in progress on other islands. Police, firemen, and volunteers have been deployed assisted by a drone and a rescue dog," Vassilakis said.