Nobel peace prize winner Kailash Satyarthi

Yet attempts on his life have not deterred Satyarthi from a mission to save children from slavery and end trafficking in India where he estimates 60 million children, or 6 percent of the population, are forced to work.

"I strongly believe ... that freedom is divine. Freedom is godly. God made us free. We fight for something that God has given to all of us," Satyarthi, 60, said earlier this year.

"We know that slavery in general, but child slavery in particular, is largely a neglected or ignored area. Most countries do not agree that they have child slavery," he added.

After switching careers, Satyarthi founded one of India's most well-known child rights groups, Bachpan Bachao Andolan (Save the Childhood Movement) in 1980.

He has since helped rescue more than 70,000 children from brick kilns, stone quarries, carpet loom factories, circuses, sweatshops and farms.

The activist, normally seen in a long traditional cotton kurta, has also taken on the struggle for children across the world and founded one of the world's largest civil rights movements, the Global March Against Child Labour.

On Friday he dedicated his award, shared with Pakistani rights campaigner Malala Yousafzai, to children in slavery.

"Each time I have freed a child, the child who has lost the parents and the parents who have lost all the hope that the child would ever come back, and when I hand this boy or girl over to the mother and the mother embraces him or tries to put him in her lap, I cannot explain what kind of joy one can have," Satyarthi said.

The rescue of such children is not easy, but Satyarthi's organisation has over the years managed to work closely with anti-trafficking police units and child protection agencies to save children and bring perpetrators to justice.

In one operation this May, police rescued 63 children and arrested 23 suspected child traffickers at the Old Delhi railway station, acting on a tip-off from Satyarthi.

During an extensive interview, the bespectacled, bearded activist described how children were deliberately crippled or mutilated by traffickers, put on the streets and forced to beg.

Others were stolen from villages to work as child soldiers - their books and toys taken from their hands and replaced with guns and bombs, he said.

Corruption involving law enforcement officials and powerful public figures has helped fuel slavery in India, which is a source, destination and transit country for traffickers, Satyarthi said.

"Within India, huge trafficking is flourishing," he said. "Traffickers are like the mafia. They are able to earn huge money and are able to bribe the law enforcement authorities so when we try to free those children, or oppose those perpetrators in the court, then it's always dangerous."

A global index on modern slavery last year showed that of an estimated 30 million people who are enslaved worldwide, trafficked into brothels, forced into manual labour, victims of debt bondage or born into servitude, half are in India.

Satyarthi's organisation has lobbied for more protection to be provided to rural children and women who are trafficked to cities to work as domestic workers in middle class homes.

Last month, based on a complaint filed by Bachpan Bachao Andolan, the government was forced to put in place regulations to protect maids, who are often physically and sexually abused.

One seven-year-old girl Satyarthi rescued from a stone quarry had been born into slavery. The girl had seen her mother raped as punishment after her father tried to escape, and her brother died in her lap for lack of medical treatment.

"Why didn't you come earlier?" she asked him angrily.

In another anecdote, Satyarthi recalled overhearing three former child labourers from India, Nepal and Bangladesh comparing how much they had been sold for.

Two had been sold for $50 and the third for $100.

"I was listening carefully to their conversation and suddenly one of them asked the other: "Do you have any idea how much a buffalo costs?" Then they talked and one of them replied: "It is no less than 50,000 rupees ($815).

"That means a buffalo cost 10 to 20 times more than a girl. This is the reality they were talking and discussing amongst themselves and I was almost crying."

Human rights groups, the United Nations and Prime Minister Narendra Modi were among those that showered praise on Satyarthi as the news of the Nobel Peace Prize emerged.

The tall softly-spoken activist remained modest when asked whether he was surprised by winning the Nobel.

"I never really thought about it, but people used to tell me that since you have started this task in India it has become a worldwide movement and one day you will get this kind of an honour," he told reporters who had thronged his office in Delhi.

"But I never gave it much thought..."