Officials are searching for a Romanian tourist who went missing at sea while diving in Thailand.

Search teams are scouring the waters off Koh Kaew Nok island south of Phuket to find Sebastian Emil Somesan, 46, after he failed to resurface from freeing a snagged boat anchor during a diving trip.

Somesan had invited fellow Romanian Alexandru Florin Miron, 47, and his Thai friend Saowalak Kanhawong to go diving around the island on January 8.

They departed Nai Harn Beach on Somesan's speedboat in the morning. After they completed the dive, however, they were unable to depart as the boat's anchor had been wedged in rocks under the water.

A fairly experienced diver, Somesan plunged to a depth of around 30 metres to release the anchor, but never returned.

Miron himself could not jump in to search for him as he had only been diving for three months. He phoned his wife Nichkamol Theparak, 42, at 12:45 pm asking to send lifeguards from Rawai for help.

She said: 'He told me that he had a problem as Somesan did not come back after diving for a while. So I got a lifeguard's number from a rescue organisation and had them to talk to my husband.'

A search command centre was set up at Yannui beach, with the Thai navy, marine police, local officials, divers, and volunteers joining the operation.

Somesan often travelled to Phuket, where his wife Sangrawee Sringa, 42, and his daughter lived.

Local media reported that Phuket Governor Narong Woonciew has been briefed about the missing diver.

The governor said: 'Everyone should exercise caution while in the water. There are still strong currents even though we are at the end of the southwest monsoon season.'

Search and rescue efforts are still ongoing.