Hundreds of people from across northern India had their kidneys removed at a private house, which had a state-of-the-art operating theatre hidden inside, after being lured to Gurgaon.

Several people have been arrested, including some doctors, police said.

The case, one of the largest transplant rackets reported in India in recent years, has dominated the country's headlines and sparked calls for the government to tighten regulation of kidney transplants to stop backstreet operations as global demand rises. The doctor accused of heading the group may have fled the country, according to police, quoted as saying he appeared to have been tipped off. As many as 50 medical officials may have been involved in the racket.

At least five foreigners -- two U.S. and three Greek citizens -- were found in a luxury guesthouse operated by the doctor running the racket, Lal was quoted as saying by local media.

Police said they have since been allowed to leave India.

Many victims complained they were taken to the house with promises of a job, and then duped or forced at gunpoint to sell their kidneys.

Labourers, many who gathered every day in parts of Gurgaon to look for any kind of job, were offered around Rs 50,000 for their kidneys. They were sold to wealthy clients for 10 times as much.

"I was approached by a stranger for a job. When I accepted, I was taken to a room with gunmen," Mohammed Salim told a TV channel.

"They tested my blood, gave me an injection and I lost consciousness. When I woke up, I had pain in my lower abdomen and I was told that my kidney had been removed."

Suspicious neighbours said they had noticed blood running out of the house's gutters, as well as blood-soaked bandages and even bits of flesh thrown into an open plot near the house.

Kidney failure has become more common in rich countries, often because of obesity. But a shortage of transplant organs has fuelled a black market that exploits needy donors.

In ‘transplant tourism’, rich patients pay tens of thousands of dollars to receive kidneys in poor countries, where payments are typically about $1,000 in the black market.

Illegal transplants are not new in India.