CCTV images have been released showing missing British TV doctor Michael Mosley around 20 minutes after he was last seen by his wife on a Greek island earlier this week.

The 67-year-old left his wife on a beach on the island of Symi around 1:30pm on Wednesday, local time.

Mosley set off from Agios Nikolaos beach towards the fishing village of Pedi.

The CCTV images appear to show Mosley wearing a cap and holding an umbrella in the main street of Pedi at 1:52pm.

The images, released by police, could shed some light on what happened to Mosley after leaving the beach.

Officials were concerned Mosley may have come into harm while walking along the rocky coastal path to Pedi, but the CCTV images dispel that theory. 

Symi's mayor Lefteris Papakalodoukas said people had also seen Mosley walking through the town with an umbrella.

"We have eliminated the possibly he had an accident along the footpath [to Pedi] ... but we've lost him from here onward because there are no more cameras," he told the BBC.

The search for Mosley had ramped up earlier on Friday, with divers reportedly joining police, firefighters and volunteers.

A sniffer dog, drones and a helicopter are also being used in the search.

British media is reporting Mosley's four children have also travelled to Symi.

Mosley is well-known in Britain and Australia for popularising the intermittent fasting diet and rose to fame with appearances on the BBC.

He has also appeared on television shows filmed in Australia. 

Mosley had been holidaying on the island with his wife Clare Bailey, who reported him missing when he did not return from the walk. 

Concerns for Mosley's safety have been amplified as temperatures in Symi have been extremely high this week, reaching around 40 degrees Celsius.

The picturesque island of Symi sits on the eastern side of the Aegean Sea, about 6.5 kilometres from Türkiye's coast. 

The rocky island is 16km long and home to about 2,500 residents.