By Sandeep Sahu
BBC News, Bhubaneswar
The chain stretched for as far as the eye could see
Thousands of people, a majority of them tribal, have formed a 17km (10.5 miles) human chain around hills in the eastern Indian state of Orissa.
They were protesting against plans to start bauxite mining in the hills by a UK-based multinational company.
Reports from Lanjigarh, about 600km from the state capital, Bhubaneswar, said over 10,000 people encircled the Niyamgiri hills.
The Supreme Court last year said two huge mining projects could proceed.
The ruling meant that an arm of the British-listed mining giant Vedanta could use bauxite from a mountain in Orissa which local hill tribes view as sacred.
Bauxite is regarded as one of the world's most important aluminium ores.
Some of the protesters carried bows and arrows
In a separate ruling last year, South Korean steel firm Posco was also given the go-ahead by the court for a $12bn plant in the same state.
Environmental and tribal campaigners have called on India's prime minister to halt the Vedanta project.
They argue that India's rush to development should not come at the expense of traditional and sustainable ways of life of tribal and marginalised people.
Many who took part in Tuesday's protest brandished traditional weapons, such as bows and arrows. They carried placards with slogans including "Vedanta, Go Back" and "Stop mining in Niyamgiri".
Their demonstration was followed by a public meeting in which speakers railed against the London-based company, which is currently setting up a large alumina refinery in the area.
Speakers said they would oppose mining in the hills until their "last breath". They demanded the immediate cancellation of the mining lease to Vedanta.
"The Niyamgiri hill is the lifeline of the tribals and there is no way we can allow bauxite mining here," Lingaraj Azad, a leader who spoke at the meeting, told the BBC.
The Dongria Kondh tribe, who live in the Niyamgiri hills, consider the hill sacred. They have been opposing the mining lease given to Vedanta for years, saying it would destroy their lives, livelihood, religion and culture.
Environmentalists have also opposed plans to start bauxite mining, because they say that the area is ecologically sensitive.
They say that if mining goes ahead it would lead to the destruction of forest, large scale displacement and would dry up or pollute dozens of rivers and streams.
Vedanta officials, however, have consistently denied the allegations.
"Far from drying up streams, it will in fact lead to an increase in the ground water level," said Mukesh Kumar, head of the company's mining operations in Lanjigarh.
Mr Kumar also dismissed suggestions of large scale displacement as a result of the mining operations.
"No-one is going to be displaced. We are committed to sustainable development of the area," he said.