An Indian copper smelter at the centre of a police shooting that left 13 protesters dead has been granted permission to reopen by the country's environmental court.

The Sterlite plant, owned by British mining giant Vedanta Resources, was closed after the bloody police crackdown in May on protesters who say the smelter is poisoning the air and water.

Vedanta Resources, owned by Indian-born billionaire tycoon Anil Agarwal, had appealed against the plant's closure by the state government of Tamil Nadu where it is located.

The National Green Tribunal, a federal authority which rules on environmental matters, ordered Saturday that the plant in Thoothukudi city could resume operation.

Sterlite CEO P. Ramnath on Sunday welcomed the decision.

"We are happy that all those affected by the closure will get back their source of livelihood and the town of Thoothukudi will revert to normalcy," he said in a statement on Twitter.

The Tamil Nadu state government has said it will appeal the decision in India's highest court.

The city of Thoothukudi, previously known as Tuticorin, had been rocked by long-running protests over the plant, one of the largest in India.

Protesters say it harms the environment and the health of those living near it, claims the company has long denied.

The demonstrations intensified in May after Vedanta sought to double the annual capacity of the plant.

On May 22, police opened fire on thousands of protesters, killing 13 people.

The plant was shuttered by the state government in the aftermath of the shooting.

The company denies all charges and maintains that it adheres to the best environmental standards.

The federal green court ordered Vedanta to spend one billion rupees ($13.9 million) over three years to assist local communities.