A new U.N. report says 2014 was marked by harrowing accounts of rape, sexual slavery and forced marriage being used by extremists including the Islamic State group and Boko Haram.

The report by Secretary-General Ban Ki-moon released Monday urges the Security Council to recognize that sexual violence can not only be employed as a tactic of war but as a tactic of terror.

The report expressed "grave concern" at sexual violence perpetrated by armed groups, including those promoting extremist ideologies in Iraq, Syria, Somalia, Nigeria, Mali, Libya and Yemen.

It said efforts "to degrade or destroy" the Islamic State group, Boko Haram, al-Shabab, Ansar Dine and al-Qaida affiliates "are an essential part of the fight against conflict-related sexual violence."

The report focuses on 19 countries where sexual violence occurs.