Indian Nobel peace laureate Kailash Satyarthi on Monday started a cross-country march aimed at forcing authorities to clamp down on the widespread sexual abuse and trafficking of vulnerable children.

Satyarthi and scores of supporters embarked on the “India March” at Kanyakumari on the country’s southernmost tip. He hopes to get one million people involved in various stages of the march to New Delhi.

“If our children are not safe in India, if our children are not safe in schools, then we have to change it,” 63-year-old Satyarthi told NDTVtelevision.

“We cannot just wait and watch. One cannot be a silent spectator,” he said, calling child sexual abuse a “growing menace, a growing epidemic”.

The march will finish in New Delhi on October 16 after he and his supporters travel across all 29 states and seven union territories, covering 11,000 kilometres (6,835 miles).

More than 9,000 children were trafficked in India in 2016, up nearly 25 percent from the previous year, according to the Ministry of Women and Child Development.

About 14,000 children were victims of rape and sexual harassment in 2015, data from the National Crime Records Bureau showed.

But those figures may only be the tip of the iceberg, with experts saying the government underestimates the numbers in a country where a shroud of silence surrounds such crimes.