The prosecutor of the world's only permanent war crimes court warned late Friday she was ready to act if wide-scale abuses were committed in Burundi, which has been rocked by months of political unrest.
"Any person who incites or engages in acts of mass violence ... is liable to prosecution before" the International Criminal Court, prosecutor Fatou Bensouda said.
Burundian President Pierre Nkurunziza's determination to end months of protests over his rule, which were sparked by his successful quest for a controversial third term in office, has sparked deep international concern.
With almost daily battles in the capital Bujumbura between gunmen and security forces, Nkurunziza has issued an ultimatum to Burundians to hand over illegal firearms by Saturday night.
Bensouda slammed what she called "highly troubling and incendiary rhetoric" by high-level officials in the central African nation surrounding the deadline.
She said she had told Burundian leaders that if there is any conduct "whether by security forces, militias or any armed forces" that could "amount to war crimes, crimes against humanity or genocide, no-one should doubt my resolve to fulfil my mandate so that the perpetrators do not go unpunished."
Bensouda reminded all sides in the upheaval that "Burundi is a state party to the ICC" and that the court therefore had jurisdiction over war crimes "committed by Burundian nationals or on the territory" of the country.
The ICC was set up in 2002 to investigate and try those responsible for genocide, war crimes and crimes against humanity, where national authorities cannot or will not prosecute.
The United States joined the international chorus of alarm at the deteriorating situation in Burundi on Friday, accusing the government there of inciting violence.
At least 200 people have died in the turmoil and 200,000 fled the country, recalling the climate in the run-up to the country's 1993-2006 civil war, in which an estimated 300,000 people were killed.