Chennai, India - Three years ago, Vikas was a school dropout helping his father till the family farm near the northern Indian city of Kanpur - a job he despised.

But today, his fortunes have changed. The 26-year-old is earning much more money working as one of the hundreds of kidney brokers across the Indian subcontinent, fuelling an ever-expanding multimillion-dollar black market for the sought-after human organ.

"If you have the money and want it fast, you come here. I will find you a donor and you can go home with a new kidney in a month," Vikas told Al Jazeera, speaking on the condition that his real name not be published.

According to the World Health Organisation (WHO), South Asia is now the leading transplant tourism hub globally, with India among the top kidney exporters. Each year more than 2,000 Indians sell their kidneys, with many of them going to foreigners.

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Aadarsh, a Mumbai-based agent who also demanded anonymity to protect against police reprisals, said "his kidneys" have gone to recipients from Canada, Israel, Britain, Saudi Arabia, the United Arab Emirates and Bahrain, although more and more buyers were now coming from within India.

An alarming surge in renal diseases, diabetes and high blood pressure is driving the global demand for kidneys, which greatly exceeds supply. The near-universal ban on the sale of human organs, coupled with a widespread reluctance in many cultures to donate kidneys even after death, means that patients often must spend years hooked up to dialysis machines - unless they can find a willing donor.

This gaping hole between demand and the legal supply of kidneys is being filled by what may be the world's biggest black market for organs, which criss-crosses India, Nepal, Bangladesh, Pakistan, Sri Lanka and Iran.

However, in recent years, Sri Lanka's capital Colombo has become the new nerve centre of this network, where most transplant operations are carried out. In recent years, Sri Lanka has attracted kidney buyers from as far afield as Israel and the United States.

This development came after India tightened its rules on organ exchanges in 2008, following the arrest of a "kidney kingpin" running one of the world's largest kidney trafficking rings. Many donors are also taken to Iran, the only country in the world where selling kidneys is legal, though not to foreigners.

Anurag, one of the top names in brokering circles, told Al Jazeera that many agents in India and Bangladesh were working at the behest of individual doctors or hospitals based in Colombo who offered "complete packages" to foreign recipients, with prices ranging from $53,000 to $122,000.

"It covers everything - hospital bill, doctor's fee, payment to the donor, his travel and accommodation cost, and, of course, broker's commission. This is the best way because it saves everybody time and hassle," Anurag - who also wanted his real name withheld to avoid trouble - told Al Jazeera from Sri Lanka.

Social media's role

Although the illicit racket has flourished since the 1990s, social media has catapulted the trade into a new dimension. Brokers like Vikas and Aadarsh are openly lurking on dozens of Facebook pages fashioned as kidney and transplant support groups.

Once the demand for a particular match is relayed to the broker, all it takes is a single post promising monetary compensation in exchange for a healthy kidney. The messages often look like as if they are posted by a "distressed relative" who is urgently looking for a particular blood-match donor, suggesting a quick transaction.

Vikas was masquerading as a young woman called Priyanka Singh on several forums when Al Jazeera first contacted him.

"They always trust a young, nice-looking woman more. When anybody calls, I tell them she is my sister. In the past, I have also used English names. People think they are dealing with foreigners and, therefore, will get more money," he said.

But operating on social media comes with a strict set of rules, too. "I create new aliases every five to six weeks and discard all the mobile numbers used with it. I avoid meeting anyone until I am sure it's not a trap. Also, I never respond to people who have contacted me once before. You won't be able to find me next month," Vikas explained.

The brokers told Al Jazeera they mostly target healthy and non-smoking donors in their 20s or early 30s, preferably men, since they can more easily travel abroad alone. Those who already have passports are given preference. Once trust is established, the potential donor is then sent for pre-arranged blood tests and a tissue-typing test in chosen pathology laboratories across New Delhi and Uttar Pradesh.

Those in the southwest of the country are usually sent to a large, private speciality hospital based in Chennai. Some of the doctors there are part of the Colombo network and help to speed up the process.

"The labs send me the test reports, but in some instances, they send them directly to the doctors in Colombo. Someone based in Chennai pays for the tests. If the match is good, I make arrangements for the donor's travel to Colombo," said Vikas. "I get all the documents ready, including the passport if required. I have contacts who can arrange things within days."

Big money

Vikas is often required to escort the donors to Mumbai. He usually arranges to meet them, sometimes for the first time, at the New Delhi railway station, from where they take the train to Mumbai. "If the donor is from a poor family, has no education or exposure, they are reluctant to travel alone," he said.

"I am instructed to drop them at hotels or guesthouses at fixed locations. My money is always left at the reception. Sometimes I have also dropped them at ISD phone shops and walked away without looking back, as per instructions. I take my commission and never see the donor again. The donor goes to Colombo with another agent for the operation," Vikas said.

His first donor earned him a commission of 25,000 rupees ($380) three years ago, but now he makes 50,000 to 80,000 rupees ($757-$1,211) per donor. Last year he made eight deals, earning more than half a million rupees ($7,700).

According to the brokers, donors who already possess passports are paid roughly 400,000 rupees ($6,000), part of which is paid two days before the operation. Others whose passports are arranged by the brokers receive up to 300,000 rupees ($4,500).

Both the donor and broker usually stay at a luxury apartment complex in Colombo only a kilometre away from one of the three hospitals openly catering to "international clients". The donors normally return home in 18-25 days.

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"A surgeon once told me he was getting 300,000 Sri Lankan rupees [$2,160] per operation. Senior consultants can ask for even higher amounts. The private hospitals also regularly pay immigration officials at the airport for a 'no-questions-asked' entry into the country. They know people travelling with me are donors when they ask for a tourist visa on arrival," Aadarsh said.

In 2011, Sri Lanka banned its nationals from donating kidneys to foreigners after the allegations surfaced that illegal kidney transplants were taking place.

But foreigners can still opt to have transplants performed on the island nation if they bring in their own donors. Even though Sri Lanka's health ministry insists that both donor and recipient must be from the same country, its top bureaucrats conceded that it was very difficult to enforce that rule and ascertain that "no money was changing hands".

Repeated requests for comment from the Sri Lankan government went unanswered.

Although the brokers mainly work for the well-oiled and sophisticated network in Sri Lanka, they claimed other smaller rings could offer cheaper transplants too.

"If your budget is tight, you can get a kidney for 1.7m rupees ($25,700) in West Bengal. There are local agents who get their supply [donors] from Nepal or Bangladesh. But I don't do that deal because I want more money," Vikas said.

So why doesn't he go to Sri Lanka like other brokers to earn a higher commission?

"I will never go there. They pay me well, but I don't trust them. Look at me, I would be an ideal donor. What if they took out my kidney?"

Follow Nishtha Chugh on Twitter: @NishChugh