Rescuers continued searching for British TV presenter Michael Mosley on the mountainous Greek island of Symi on Saturday, the third day of a wide operation launched after he was reported missing by his wife.

The 67-year-old doctor and healthy living advocate, who has endorsed fasting and offered tips on sleep and diet, was last seen at 1:30 pm (1030 GMT) on Wednesday.

He disappeared after he set out on a stroll in searing temperatures along a rocky coastal path from Agios Nikolaos beach to the village of Pedi. Mosley did not have his mobile phone with him, hampering tracing efforts.

Police, the fire brigade, the coast guard and volunteers have been searching on and off the island in the eastern Aegean assisted by a helicopter, drones and rescue dogs.

On Saturday, police searches shifted focus to another rocky area, between Pedi and the beach of Agia Marina, after video footage showed Mosley walking through the village of Pedi.

"The search continues," said spokeswoman Constantina Dimoglidou. "We are investigating on foot another rocky part, the wider area of Agia Marina."

Divers were also involved in the operation and vessels sailing nearby were on alert.

Images from a security camera in Pedi showed what is believed to be Mosley, strolling by at 1:49 pm on Wednesday, holding a sun umbrella, suggesting he may have made it safely off the coastal path.

Symi Mayor Lefteris Papakalodoukas said that the images and video footage from security cameras had helped sketch out what authorities believed was Mosley's possible route, which he described as "unconventional."

They indicated that he may have continued further through Pedi into another challenging area around Agia Marina, the mayor said.

Mosley has appeared on well-known UK TV programmes including Trust Me, I'm a Doctor, The One Show and This Morning. (Reuters)