Activist Medha Patkar has threatened hunger strike

They were rallying against a recent judgement by the Supreme Court, which permits an increase in the height of the Sardar Sarovar dam over the Narmada river.

The ruling followed years of protest by environmentalists who say the dam will displace thousands of families.

Hunger strike

Medha Patkar, leader of the Narmada Bachao Andolan (Save the Narmada Movement) which has spearheaded the protests, termed the court ruling "anti-people", "illogical" and "pro-capitalist".

She said she would be going on a hunger strike against the decision from Wednesday.

I will continue to create awareness among the people against the judgement by writing against it

Booker prize winner Arundhati Roy

Her decision received support from fellow campaigner and 1997 Booker prize winner Arundhati Roy.

"I will continue to create awareness among the people against the judgement by writing against it," Ms Roy told the French news agency AFP.

The Narmada Bachao Andolan says that the construction of Narmada Dam would displace 200,000 people, apart from damaging the fragile environment of the region.

But the government says the dam would help provide drinking water and irrigation for millions of people in a drought-prone area.