The victims are usually teenage girls

South Asia provides most of the 500,000 women and children trafficked each year in Asia, Unicef estimates.

"It is one of the blights of South Asia. The situation is getting out of hand," Unicef regional director Sadig Rasheed said in Sri Lanka.

He said many problems could be stopped "tomorrow" if men said no to child sex.

"While many of those represented by these daunting figures may end up in other forms of hazardous and harmful labour, a significant proportion of the young ones will be providing sexual services."

'Slavery'

Referring to a "rising tide of commercial sexual exploitation" in the region, Dr Rashid said numbers being trafficked in Asia represented nearly half the world total - and South Asia was bearing the brunt.

There should be no hiding place for those selling and trading children for sex Dr Sadig Rasheed Unicef

"We are facing a very serious situation here in South Asia. The situation is nothing short of, I would say, modern-day slavery,"

He told journalists in the Sri Lankan capital, Colombo, that the child sex trade in the sub-continent was largely for locals.

"It is a market to satisfy South Asian men.

"There are also incidences of boys being traded for sex, such as in Sri Lanka where foreign paedophiles lure beach boys with money."

Dr Rashid said not all of those trafficked worked in the sex trade, but "a considerable proportion will have become involved in such exploitation".

'How very sad'

Because of links with organised crime, it was extremely difficult to get accurate statistics on how many people were being trafficked and commercially sexually exploited, he said.

"It seems that more and more women and children are leaving countries like Nepal and Bangladesh and many are ending up being abused in a highly lucrative sex trade."

War in countries such as Nepal and Afghanistan was making matters worse, as thousands of young people left in search of a better future - and ended up in the sex trade.

"How very sad. What an indictment. What a complete failure for family, government and of us all," Dr Rasheed said.

He urged governments who had signed a global anti-child trafficking drive in Japan in 2001 to tackle poverty and inequality which, he said, lay at the root the problem.