World-famous Indian guru Sri Sri Ravi Shankar has come under fire for a mass festival to promote peace that environmentalists say risks damaging the delicate ecosystem of Delhi's Yamuna river.

Critics say the World Culture Festival, to be held later this month on the banks of the river with millions of fans including India's prime minister in attendance, will cause lasting environmental damage.

Organisers say they expect 3.5 million people to attend the three-day event, which will feature yoga and meditation sessions, peace prayers by Sanskrit scholars and traditional cultural performances from around the world.

"Three and a half million people are going to trample the area so basically 210,000 tonnes of weight will be put on a fragile ecosystem," said activist Anand Arya, who has asked India's top environmental court to cancel the event.

"It is most unfortunate that the event is being organised by an apostle of peace and non-violence."

Manoj Mishra of the Live Yamuna campaign to protect the river that flows through the capital, said more than 1,000 acres (405 hectares) had been cleared to make way for a stage, pontoon bridges, portable cabins and parking.

"Reed beds were cleared, vegetation was chopped for a two-and-a-half day event which will leave an ever-lasting impact on the environment," Mishra said.

Shankar's Art of Living foundation, which is organising the festival, denied there would be any permanent impact and said it had secured permission from all the necessary authorities to hold the event.

"We have used only eco-friendly material like wood, mud, cloth, and scaffolding towards building a temporary stage," the foundation said in a statement to AFP.

The event, due to start on March 11, is billed as a platform "for spiritual and religious leaders, politicians, peacemakers and artists to spread the message of global peace and harmony in diversity".

The globe-trotting Shankar, once ranked by Forbes magazine as India's fifth most powerful person, is close to Prime Minister Narendra Modi and the pair have meditated together.

The Yamuna river is the largest tributary of the Ganges, considered holy by Hindus.

Despite high levels of pollution, its floodplains are rich in flora and fauna with more than 320 bird species and 200 types of plants.

On Monday a committee appointed by the environmental court recommended fining the foundation $17.5 million dollars but did not say the event should be cancelled.

The court will hold a further hearing into the matter on Wednesday.