Each room has the same basic elements - a couch, a large TV showing song lyrics and some microphones.

Privacy is a key element of the whole experience. When the door closes on a room, the people inside can do almost anything they want.

In many bars, it's common to find alcohol, prostitutes and drugs. And especially in southern China, ketamine is a karaoke favourite.

Using hidden cameras, we shot footage inside a private room in a seedy karaoke bar in the city of Shenzhen.

A group of young men sat in a row all dressed in tight T-shirts, their hair spiked with gel. Most held a mobile phone in one hand and a burning cigarette in the other.

Within minutes, some pull out small plastic bags filled with white crystallised powder - ketamine.

Using credit cards and plastic straws, they cut the drug into short lines on the glass coffee table in front of them.

Over and over, they cut and inhale. They've clearly done this many times before.