Over 115 million of the world's children and young teenagers, or more than 7 percent of the total, are engaged in dangerous and life-threatening jobs, said the International Labor Organization (ILO).

In a linked statement, a UN investigator said child labor was in great demand by employers because it was cheap "and because children are naturally more docile, easier to discipline than adults, and too frightened to complain."

The statement and the report were issued to mark United Nations World Day against Child Labor which falls on June 12, Reuters reported.

Extreme poverty drives practically all of them to take up both physically and psychologically dangerous jobs, sometimes where the effects from toxic substances they had to work with only emerge in later life, according to the ILO report.

Many as young as five were employed in such work although the numbers of small children involved has declined in recent years under pressure from campaign groups and public opinion. But the total number of young people aged 15-17 engaged in such work had risen sharply, it said.

The report said the largest numbers were in Asia, where over 48 million children and young people - or some 5.6 per cent of the total in the region - were earning their living in jobs fraught with danger.

The UN investigator into modern forms of slavery, Gulnara Shahinian, said "unscrupulous employers" took advantage of smaller children in often illegal artisanal gold mining.

Boys were sent down through narrow and makeshift tunnels, at a high risk of fatal accidents, while both boys and girls had to handle toxic mercury to extract gold, exposing them to irreversible damage to their health, Shahinian, an Armenian lawyer, said in a statement.

They were also exploited in the flower, banana and palm oil production industries, and in cities in loading and unloading heavy goods or collecting waste in garbage fields where they were also exposed to physical and sexual violence, she said.