Footage shows customers trying a bizarre leech therapy that is believed to improve blood circulation and relieve pain.

The unusual spa treatment called 'hirudotherapy' uses medical leeches to suck a small amount of blood from the patient's body.

Bloodsucking worms are seen in the video attached to a client's back and gorging themselves on his blood at the Baan Khun Suk clinic in Bangkok, Thailand.

Each session lasts between 45 minutes to an hour, with a different set of leeches used per customer, staff said.

A clinic spokesperson said: ‘Every patient gets fresh leeches for the treatment. The therapy improves blood circulation, reduces swelling and also offers pain relief for the patients.

'It might look scary at first, but the treatment is not painful at all. It feels like an ant bite. Many of our patients feel instant pain relief after each session.'