Last year, there were 69 allegations of child rape and other sexual offences by peacekeepers from 10 missions.
One advocacy group says it has passed on new reports to the UN that a soldier made four girls have sex with a dog.
The UN said it was looking into the "exact number and nature" of the claims.
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The new reports of abuse were made by the Code Blue campaign run by the advocacy group Aids-free World. The group says the abuse was reported to have happened between 2013 and this week.
It says the bestiality claims, dating back to 2014, involved a commander with French forces. The girls, one of whom later died of an unknown disease, were each paid 5,000 Central African francs ($8.60; Â£6), the report says.
Other allegations centre on troops from France, Gabon, the CAR and the Democratic Republic of the Congo. Forces were deployed in 2014 to help restore order in CAR after the president was overthrown the previous year and sectarian violence gripped the country.
A UN statement on Wednesday said the allegations involved some of its staff, as well as non-UN peacekeepers.
Teams were now on the ground investigating the reports, it said, while alleged victims will receive counselling and medical help.
Earlier this month, the UN Security Council adopted a resolution calling for the repatriation of peacekeeping units whose soldiers face allegations of sexual abuse.
Last August, the UN envoy to Central African Republic (CAR), Babacar Gaye, was sacked amid multiple allegations of sexual abuse by peacekeepers.
An independent panel called the UN response to the allegations "seriously flawed" and a "gross institutional failure".
It accused senior UN officials of abusing their authority by failing to take action over allegations of abuse by soldiers from France, Equatorial Guinea and Chad.
UN officials say they are investigating "extremely troubling" claims of sexual abuse by peacekeepers in the Central African Republic (CAR).