By Waliur Rahman BBC correspondent in Dhaka

Children are often the most vulnerable to trafficking

A three-day conference began in the Bangladeshi capital, Dhaka, on Tuesday, and is focusing on traffic in women and children in particular.

The organisers of the meeting say they hope to improve general understanding of the trade in humans, which has become a highly profitable business.

They say at least 20,000 women and children are being trafficked from the region every year, ending up mainly as prostitutes and forced labourers.

Crisis

The conference - hosted by the International Organisation of Migration (IOM) - is being attended by representatives from Bangladesh, India, Pakistan and Nepal.

The suffering of the victims of trafficking goes on day in and day out for years Jorgen Lissner UNDP

The organisers say that between 700,000 and two million people are being trafficked globally each year - a business worth $12bn.

Only the illegal trade in drugs and small weapons is more lucrative.

The main destination of people from South Asia is the Middle East, but many stay within India and Pakistan.

Often driven by poverty, most trafficked people end up in prostitution, forced labour and domestic help.

The IOM's regional representative, Shahidul Islam, said: "There is a dark side of population mobility known as trafficking in persons."

Slaves

Despite wide coverage and many initiatives over the last two decades, he said, human trafficking remained a largely unexplored area.

People are often forced into unpleasant work

United Nations Development Programme (UNDP) officials say the victims of trafficking are simply slaves in an unknown place far away from home.

The UNDP's resident representative in Dhaka, Jorgen Lissner, said human trafficking ranked along with murder and rape as one of the cruellest crimes known to humanity.

"The suffering of the victims of trafficking goes on day in and day out for years, forced into activities that are backbreaking, either physically or emotionally and with no hope," he said.

The Dhaka meeting will explore "second generation" concepts to identify the emerging parameters of human trafficking.

It will also try to explore new ways in which South Asia can reduce, and ultimately eradicate, human trafficking.