A rotting carcass of a whale that washed up on an Indonesia shore has been found to contain almost six kilograms of plastic waste in its stomach.

The garbage inside the 9.5-metre sperm whale comprised 115 plastic cups, four plastic bottles, 25 plastic bags, two flip-flops, a nylon sack and more than 1000 other plastic pieces, according to the Associated Press.

The whale, found near Wakatobi national park in South-East Sulawesi province, was reported by environmentalists to park officials after local villagers had begun butchering the carcass.

The cause of the whale’s death has not yet been determined because of its advanced state of decay.

However, Dwi Suprapti, a marine species conservation co-ordinator at WWF Indonesia told AP that “the facts that we see are truly awful”.

A recent study published in the journal Science ranked Indonesia, an archipelago with a population of 260 million, as the second-biggest producer of plastic waste after China.

About 1.29 million of the 3 million tonnes of waste it produces yearly ends up in the ocean, according to the study.

The whale’s discovery had motivated the Indonesian government to take on tougher measures to protect the ocean, Luhut Binsar Pandjaitan, Indonesia’s co-ordinating minister of maritime affairs, told AP.

The whale carcass is examined. Photo: AP

Mr Pandjaitan, who has campaigned for less use of plastic, said this had also highlighted the need for residents to take personal action to reduce waste production.

“I’m so sad to hear this,” Mr Pandjaitan said. “It is possible that many other marine animals are also contaminated with plastic waste and this is very dangerous for our lives.”

He noted the government was already working to reduce pollution by urging shops to give up supplying plastic bags and educating students nationally about the issue. This would help it meet a target of reducing plastic use by 70 per cent by 2025.

“This big ambition can be achieved if people learn to understand that plastic waste is a common enemy,” he said.