The International Criminal Court in The Hague said it has opened a formal investigation into allegations by four people who say they were subjected to sexual abuse by a court staff member working in the Democratic Republic of Congo.
The war crimes court said on Friday it is "profoundly concerned by these grave allegations'' and had taken steps to protect the alleged victims.
It said the investigation was aimed at "establishing the facts underlying the allegations and fairly determining any possible responsibilities."
It is not clear whether the allegations will lead to a prosecution, and if so, where it would take place.
The court said it would turn the inquiry's findings over to ICC "judges and relevant parties to the proceedings concerned'' - presumably meaning legal authorities in Congo.
'Held to account'
The Coalition for the ICC, an umbrella organisation of civil society and human rights groups that support the court, said in a reaction that members had been "deeply shocked and concerned" to hear of the allegations.
"The Coalition expects the court to carry out a credible and impartial investigation into the allegations and, should they prove true, ensure that all those responsible be held to account, including, if relevant, those responsible for managerial oversight of the personnel accused," it said in a statement.
The charges come at a war crimes court that has made a priority of prosecuting rape and sexual conscription in conflict zones. Sexual abuse is rife in the volatile east of Congo, and several ongoing cases stem from the region.
Warlord Bosco Ntaganda faces charges of rape and sexual enslavement and militia leader Germain Katanga is on trial for charges including rape and sexual enslavement.
The ICC, the world's first permanent war crimes tribunal, came into being
in 2002 and the treaty that created it has been ratified by 121 nations. Prosecutors have so far indicted suspects in seven different countries, all of them in Africa, including Congo, Sudan, Kenya, Libya and Ivory Coast.