UN Secretary-General Antonio Guterres said on Monday that indiscriminate attacks "killing, injuring and terrorizing civilians" in Sudan could amount to war crimes and crimes against humanity and sounded the alarm on escalating fighting in North Darfur.

"The latest reports of escalating hostilities in El Fasher - the capital of North Darfur - are a fresh cause for deep alarm," he told reporters, marking one year of conflict in the country.

"Let me be clear: Any attack on El Fasher would be devastating for civilians and could lead to full-blown intercommunal conflict across Darfur."