A plankton bloom believed to be caused by climate change has killed thousands of dead fish that washed ashore in southern Thailand on Thursday.

Scores of the dead sea creatures - mostly tiny ponyfish - covered a four-kilometre stretch of the idyllic Thung Wua Laen Beach in Chumphon province on June 22.

Watcharin Suwapit, deputy chief administrator of the Saphlee Subdistrict Administrative Organisation, said the fish are believed to have been overcome by the mass plankton bloom.

Watcharin said: 'This algae bloom occurs once or twice a year for about three days. It is difficult to prevent or control. There are around 10 tonnes of fish that died this time. Saphli Beach in the north might be next because of the northward sea currents.'

Experts believe the phenomenon was amplified by climate change and global warming.

Speaking to local media, Thon Thamrongnawasawat, deputy dean of the Faculty of Fisheries at Kasetsart University, said: 'Various natural phenomena, such as coral bleaching or plankton bloom, have naturally occurred for thousands to tens of thousands of years. However, when global warming occurs, it intensifies and increases the frequency of existing phenomena.'

Residents flocked to the beach to collect some of the fish, shrimp, and crabs to eat for dinner.

Prayut Rattanawan, Head of Administration Chumphon Provincial Fisheries Office, and Bunyawat Thonghom from the Pathio District Fishery office have collected seawater samples for testing.

Bunyawat said: 'We advise the locals not to consume the fish as the algae might be toxic, but using them as fertilizer is OK.'

Marine heatwaves this year have also triggered fish kills in the coasts of Texas, Australia, and parts of England like Salford Quays.

Plankton, or microalgae, are tiny organisms that live in the water, both in the ocean and in freshwater bodies. They are unable to swim against currents, so they drift with the water.