Two British tourists in their 20s have been murdered in a bloody attack on a beautiful Thai beach.

The victims were a 23-year-old woman from Great Yarmouth, Norfolk, and a 24-year-old man from Jersey, in the Channel Islands, according to the Thai authorities.

The attack happened on the popular small island of Koh Tao, which is known for its diving and lively bars.

A blood-stained hoe was found near the bodies and was thought to be the murder weapon.

Police colonel Prachum Ruangthong said: "The man was chopped in the back and on the side of his head, while the woman was chopped in her face.

"It's very gruesome."

Investigators were checking CCTV from local bars and restaurants and it was reported people were prevented from leaving the island.

The Foreign Office said: "We are aware of the death of two British nationals on September 15 on the island of Koh Tao in the Gulf of Thailand.

"The embassy are urgently seeking information from the local authorities and consular staff stand ready to provide assistance to friends and family at this tragic time."

According to the Lonely Planet travel guides, Koh Tao welcomes thousands of visitors who "come to worship the turquoise waters offshore". Its bright coral, sharks and rays bring in divers, hikers enjoy jungle walks and the bar scene "rages on until dawn".

The horrific murders could badly damage tourism in Thailand which has already been affected by the country's deep political crisis and the introduction of martial law.

The bodies were found 100 metres away from the scene of a beach party, according to a local report.

It was believed that attackers may have been waiting to target the pair as they walked off at the end of the party, which was attended by a group of international revellers.