The International Criminal Court (ICC) prosecutor said Friday she would seek an extensive probe into possible war atrocities and crimes against humanity that were said to have been committed during the conflict between the Nigerian government's security forces and Islamist rebel group Boko Haram.

Prosecutor Fatou Bensouda's announcement comes in the midst of increasing unrest in the West African nation's northeast region, where around 76 people were murdered by Boko Haram jihadists two weeks ago.

The six-year initial investigation by prosecutors at the ICC will dig into accusations of unlawful acts beginning with the savage crackdown on pro-European Union demonstrations in 2013-14, the Russian takeover of Crimea in 2014, and the protracted conflict in eastern Ukraine.

Global rights watchdog Amnesty International welcomed the inquiry in a statement released Friday, describing it as an "important milestone."

In a statement, Bensouda said her office had finalized a preliminary evaluation and found a "reasonable basis to believe" that Boko Haram and its splinter units had committed war crimes and crimes against humanity through torture, massacre, sexual slavery, rape, and other brutal crimes.

Bensouda disclosed that the Nigerian government has been able to prosecute primarily "low-level captured" jihadist fighters of Boko Haram, while top military officials told her they have evaluated and dismissed accusations against their own security forces.

"Following a thorough process, I can announce that the statutory criteria for launching an investigation into the situation in Nigeria have been met," Agence France-Presse quoted Bensouda as saying in a statement, issued at the global court's headquarters in The Hague.

The ICC is a court of last resort that only deliberates on cases when member nations are unwilling or unable to prosecute them in local courts.

Bensouda, whose term as a prosecutor at the ICC is coming to a close, said Friday she also was ready to seek approval for a large-scale inquiry into the conflict between Nigerian government forces and Boko Haram.

The Gambian-born ICC prosecutor specifically cited crimes perpetrated by Boko Haram, whose 11-year insurgency campaign in Nigeria has killed around 36,000 people. Around 2 million others have been displaced as a result of Boko Haram's atrocities, UN figures show.

Bensouda's office is conducting inquiries in Central Africa, Congo, Sudan, Uganda, Libya, Kenya, Mali, Georgia, Ivory Coast, Afghanistan, and Bangladesh, and a ruling on whether to probe alleged war crimes and crimes against humanity in the Palestinian territories is waiting for court authorization.