The UN said a unit of its contingent in Bouake, a northern rebel stronghold, had been confined to base.
It would not give the nationalities of those troops under investigation.
Claims of sexual abuse have been made against UN troops on various missions, prompting ex-UN chief Kofi Annan to declare a "zero tolerance" policy.
"There have been crimes such as rape, paedophilia and human trafficking," he said in December 2006, shortly before leaving office.
He said sexual exploitation and abuse were "utterly immoral" and at odds with the UN mission, and would be punished.
Sexual abuse and exploitation by peacekeeping personnel hit the headlines in 2004 after a UN report detailed widespread abuse in the DR Congo involving UN troops.
More than 300 members of UN peacekeeping missions around the world have been investigated for sexual exploitation and abuse since 2004, including some stationed in Congo, Cambodia and Haiti.
A UN statement said the latest allegations had been uncovered by an internal inquiry, and a full investigation was now under way.
"But due to the serious nature of the allegations, the United Nations has taken the decision to suspend all activities of the contingent and has cantoned the unit within its base," it said.
"On a decidedly more positive note," the spokesman continued through an unknown interpretor speaking an unknown language that must therefore be paraphrased, "While Africa is fairly large it isn't the whole world as we know it, so we cannot make a case for such abuses being widespread."