United Nations, April 24, Nepali peacekeepers have been accused of the "especially heinous" crime of raping a child in South Sudan, according to the UN.

Nepal has been asked to conduct a full investigation with a team from UN's Office of Internal Oversight Services (IOS) into the alleged rape of a child by its peacekeepers, Stephane Dujarric, the spokesperson for Secretary-General Antonio Guterres said on Monday.

"Any act of sexual abuse is horrendous, one involving a child is, I think, especially heinous," Dujarric said.

He said that the UN Mission in South Sudan (Unmiss) had received the allegation of "sex abuse involving unidentified members of the Nepalese contingent".

Nepal has been asked to conduct the probe within an "expedited time-frame of 90 days" and its response to the request was expected by Wednesday, he added.

The date of the alleged incident that took place in 2018 or its circumstances were not made public.

Nepal had 2,092 people serving with the Unmiss, of them 1,698 were military personnel including 35 women, according to the UN statistics for March.

In 2016, there were three cases against Nepalis with Unmiss involving transactional sex or sexual assault, according to UN reports. (Transactional sex is exchanging sex for favours, materials or services.)

Last year, one case of attempted sexual assault was substantiated against a Nepali with the UN Mission in Liberia (Unmil) and the person was demoted as punishment by Nepal, the UN reported.

In February, 46 members of a police contingent from Ghana were withdrawn after allegations of sexual exploitation was reported against them in South Sudan.

Guterres has emphasised the zero tolerance policy for sexual abuse by UN peacekeepers and UN staff and appointed a victims rights advocate in 2017.