UNITED NATIONS — U.N. Secretary-General Ban Ki-Moon said Tuesday the United Nations will investigate allegations by a leading children's charity that U.N. peacekeepers are involved in widespread sexual abuse of children.

The report by Save the Children UK, based on field research in southern Sudan, Ivory Coast and Haiti, describes a litany of sexual crimes committed by peacekeepers and international relief workers against children as young as 6.

It said some children were denied food aid unless they granted sexual favors; others were forced to have sex or to take part in child pornography; many more were subjected to improper touching or kissing.

"The report shows sexual abuse has been widely underreported because children are afraid to come forward," Jasmine Whitbread, chief executive of Save the Children UK, told Associated Press Television News.

"A tiny proportion of peacekeepers and aid workers are abusing the children they were sent to protect. It ranges from sex for food to coerced sex. It's despicable."

Calling the sexual exploitation of minors a "very serious issue," Ban reiterated to reporters that he has a "zero tolerance" policy for such acts by U.N. personnel.

"I think that the report is very valuable and does give us some good points to which the United Nations should continue to address this issue," Ban said. "On all these cases which have been raised, we will very carefully investigate" and will take "necessary measures" where appropriate.

Earlier, U.N. spokeswoman Michele Montas had welcomed the report. "It's fair, and I think it's essentially accurate," she said.

Montas noted the report states the United Nations has already undertaken steps designed to tackle the problem, from establishing conduct and discipline units in all U.N. missions to strengthening training for all categories of U.N. personnel. She said the United Nations also needs to strengthen its investigative capacity.

The study was based on research, confidential interviews and focus groups conducted last year. The charity emphasized it did not produce comprehensive statistics about the scale of abuse but did gather enough information to indicate the problem is severe.

The report said that more than half the children interviewed knew of cases of sexual abuse and that in many instances children knew of 10 or more such incidents carried out by aid workers or peacekeepers.

The Save the Children UK researchers, who met with 129 girls and 121 boys between the ages of 10 and 17, and also with a number of adults, found an "overwhelming" majority of the people interviewed would never report a case of abuse and had never heard of a case being reported.

The threat of retaliation, and the stigma attached to sex abuse, were powerful deterrents to coming forward, the report said.

Ann Buchanan, an Oxford University expert in statistical attempts to quantify rates of child abuse, said the topic is so taboo it is virtually impossible to come up with reliable numbers. But she said the new report provides a useful starting point.