An oil spill has spurred cleaning works on the beaches of popular resort island Koh Samet in Thailand as the beaches have turned black from the oil slick.

The incident occurred on 27 July when a leaking pipeline operated by PTT Global Chemical spilled an estimated 50,000 litres of oil into the Gulf of Thailand. The oil spill has blackened beaches at Koh Samet, a popular tourism spot about 220 kilometres southeast of Thai capital Bangkok.

Tourists have been warned away from the island and those already there were evacuated as the cleaning work continued.

Thai soldiers and volunteers wearing biohazard suits struggled to clean the oil slicks from the beaches' sand while officials said that the oil spill was affecting tourism hugely, according to Reuters.

If spread to the coast of the mainland, the oil spill could affect the fishing industry as well, the officials warned.

Meanwhile, the PTT Global Chemical authorities have apologised for the spill. The company has adopted a high-pressure water spray to remove oil stains on the rocks and has reported that oil slick at Ao Prao Beach decreased noticeably on 31 July.

Scroll down to view the photos of the latest oil spill disaster that has hit the Gulf of Thailand.