Black water flowing through a beach sparked concern among tourists in Thailand.

A stream of the dark and 'stinky' water ran through the idyllic Karon Beach on Phuket island, staining the shallows in black murk on January 16.

Holidaymakers said they were alarmed as they feared the black water was untreated sewage being illegally dumped in the sea.

Karon Mayor Jadet Wicharasorn tried to allay concerns on January 17 by claiming the discoloured water was due to black sediments carried by the high tide from the nearby Nong Han pond.

He said: 'If the water really had been polluted, the entire seawater all along the beach would have turned black.'

He said seawater samples collected in the area were found to be 'crystal clear and odourless'.

The mayor said the municipality plans to dig sediment traps at key points to keep the black particles from reaching the sea.

Meanwhile, Sanan Rakdam, the director of Karon Municipality's Engineering Division and Wastewater Treatment Office, said machines have been deployed to clean up the sediment.

He said the municipality was committed to resolving the issue and assured the public there would be no repeat incidents.