AGRA: Two miles down the road from the white marble walls of the fabled Taj Mahal, a heavyset man crouches in the dirt of a cow shed and explains how the future of India belongs to him.

Digvijay Nath Tiwari is commander of a vigilante group that claims 5,000 members in the northern city of Agra, and which cultivates informants, swarms shop owners, ambushes trucks at night and metes out extra-judicial violence, all for one cause: protecting the holy cow, an animal held sacred by Hindu beliefs.

Across the country, hardline Hindu groups have made headlines after being captured on video insulting and beating men they accuse of involvement in cow slaughter.

"Retaliation is important at times," said Tiwari, as he sat with 17 men squeezed around a straw mat on the shed floor. His cell phone contained photographs of stick-wielding men rushing to the aid of fallen cattle.

Local police say they cannot stop Tiwari's actions, laying the blame partly on lax laws.

The gau rakshaks, or cow protectors, are inflaming tensions among India's religions and castes.

They risk undermining Indian Prime Minister Narendra Modi's efforts to focus on economic advancement, even as the right-wing Hindu nationalist forces that got him elected promote their own agenda.

The implications reach far beyond the winding alleyways of Agra. Social and religious stability are key to future assumptions of prosperity in India, currently the world's fastest expanding major economy.

"India will remain one of the strongest growth stories in the region," a Goldman Sachs strategist said in April, echoing the sentiment of many foreign investors.

Yet such outlooks built on macro-analysis risk missing a ground truth: if the right-wing groups empowered by Modi's rise do not stop antagonizing minorities, then the ruling Bharatiya Janata Party's (BJP) plans for nurturing that growth will not easily come to pass.

Changing focus

Cow slaughter is illegal in most of India, an overwhelmingly Hindu nation.

However, it had long been tolerated under the Congress party, which ruled the country for most of its independent history and prides itself on protecting Muslims and lower castes who ply the meat and leather trade.

Now the Hindu nationalist BJP is in power, and that is changing as vigilante groups gain prominence. And Modi, while saying he's concerned, has been either unwilling or unable to halt their more extreme actions.

The prime minister was trained and nurtured by hard line Hindu organisations that were instrumental in his rise from the son of a train station tea seller to leader of the world's biggest democracy.

Once at the helm, however, he has focused on more pragmatic and inclusive economic issues: spurring growth and creating enough jobs for a rapidly expanding workforce.

These initiatives could be derailed by a narrower, Hindu nationalist agenda aimed at protecting symbols made sacrosanct by religious texts and countering a perceived threat of foreign influences.

In a speech on Saturday night in New Delhi, Modi lashed out at the cow protectors.

"I feel so angry at times. Some people who are engaged in anti-social activities for the whole night wear the mask of gau rakshaks in the day," he said.

A senior aide to Modi, who is approaching the halfway mark of his five-year tenure, said at the end of July that while the leader is aware of the social and economic implications, "we cannot do much to stop cow protection forces ... cow protection is integral to our core support base."

Dalits feel under siege

The violence of cow vigilante groups this year, some of it caught in disturbing videos on the Internet, has unsettled minority groups.

One clip from the western state of Gujarat shows four men, shirtless, tied to a bumper being whipped with rods.

The victims were Dalits, or Indians at the bottom of the caste hierarchy who traditionally take away cow carcasses which can then be used for leather.

In another, from the northern state of Haryana, two people are made to sit on the road and eat a concoction including cow dung.

They were reportedly Muslims, and the footage was taken during Ramazan.

While the BJP does not bank on the support of many Muslims, it does want to secure the votes of the Dalits, a caste formerly known as untouchables.

Together, the two groups account for about 30 per cent of India's population, a major consideration with important state elections due next year and a national ballot set for 2019.

Chandra Bhan Prasad, a prominent Dalit writer and adviser to the Dalit Indian Chamber of Commerce and Industry, compared the violence to that of Ku Klux Klan racism in the United States.

"It's like India's version of KKK — the past was great so long as these blacks were under our thumb, society was beautiful. So, how to control these Dalits?"

'Cow not just an animal'

The Rashtriya Swayamsevak Sangh (RSS), the nation's umbrella right-wing Hindu organisation which helped create the BJP, does not appear willing to tackle cow protection forces, blaming outlaws for causing the trouble.

"The cow is not just an animal. We have an emotional and religious attachment to it and we want to make it the centre of our economic activity," said a senior RSS leader in New Delhi, who asked not to be named so he could speak more frankly.

"Vigilantes are instructed to follow the rules and they are a disciplined force. We admire their work."

Champat Rai, a leader of the Hindu activist Vishwa Hindu Parishad (VHP), or World Hindu Council, a group formed by RSS leadership which oversees cow groups, was more direct.

"I am a cow patriot and want to free cows from the slavery of Muslim butchers," he said. "It's better we shed our blood to save the blood of cows."

In Agra, some 220 km south of New Delhi, there has already been bloodshed, and the threat of more to come.

One prominent Dalit businessmen in the city, H.K. Pippal, said recently at his shoe factory that he had a plan should the cow protection gang try to interfere with his operations and the cow leather it uses.

"I am very powerful, my workers could kill them."

Tiwari, the cow group leader, blames the butchers for much of the problem. "It's not just that the butchers get beaten," he said. "They attack us and threaten to kill us. It is a serious clash."

Tiwari acknowledged having four criminal cases pending against him, but said he was innocent in all of them.

In February this year, the vice president of the VHP in Agra, who was also a senior member of Tiwari's group, was surrounded by a group of five Muslims while walking from a temple to his furniture shop, according to a police report.

The men had previously been targeted by the cow protectors for allegedly dealing in beef, according to Tiwari.

One of them boasted: "You think that you are a big leader, we'll teach you a lesson today," said the police report.

A pistol shot rang out and the VHP official, Arun Mahour, fell dead in one of the oldest and busiest markets of Agra.

A mob of young Hindu men set out for a Muslim quarter, said the police officer in charge of the area, S.K. Sharma.

Soon, thousands of people were in the streets, Sharma said. "This almost became a riot between the Hindus and Muslims."

The fallen Hindu leader left behind two sons, aged 12 and 16. Asked about the family's future, his widow, Rajni Mahour, covered her face with the edge of a white sari and caught her breath for a moment.

The way forward, she said, was clear: "My family says that we should know to lay our life down for religion."