UN peacekeepers in the Democratic Republic of Congo have been banned from having sex with locals after claims of widespread abuse of women and girls.
Kofi Annan expressed "personal outrage" over the allegations
The new rules were disclosed in a letter from UN Secretary General Kofi Annan to the Security Council.
Mr Annan also called for 100 extra military police and French-speaking investigators to "root out" the abuse.
Claims of sexual abuse of girls as young as 13 started emerging early last year.
The victims were usually given food or small sums of money in return for sex, a report by the UN watchdog, the Office of Internal Oversight Services, said in January.
The UN has investigated 150 allegations, including gang rape, made against some 50 soldiers based in DR Congo's north-eastern town of Bunia.
It has not named the countries involved, but reports mention soldiers from Morocco, Nepal, Pakistan, South Africa, Tunisia and Uruguay, as well as a French civilian.
In his six-page letter to the UN Security Council, Mr Annan expressed his "personal outrage" at the abuses.
"I reiterate my stance - one which I know the members of the council share - that we cannot tolerate even one instance of a United Nations peacekeeper victimising the most vulnerable ones," he said.
His letter spelt out the new regulations for more than 12,000 military personnel from the UN Mission in Democratic Republic of Congo (Monuc).
The "non-fraternisation" measures included a curfew for military contingents, specialised training for all mission personnel and development of recreation and welfare opportunities "to alleviate the concentrated stress present in field missions".
Mr Annan said Assistant Secretary General Angle Kane had been sent to DR Congo to conduct further investigations.