The International Criminal Court [ICC] is investigating a surge in hostilities in Sudan's Darfur region since mid-April, including reports of killings, rapes and crimes affecting children, the court's top prosecutor told the United Nations.

"The office can confirm that it has commenced investigations in relation to incidents occurring in the context of the present hostilities," ICC prosecutor Karim Khan's office said in a report to the UN Security Council on Thursday.

ICC prosecutors are "closely tracking reports of extrajudicial killings, burning of homes and markets, and looting, in El Geneina, West Darfur, as well as the killing and displacement of civilians in North Darfur and other locations across Darfur," the report said.

ICC is also examining "allegations of sexual and gender-based crimes, including mass rapes and alleged reports of violence against and affecting children."

The regular army and paramilitary Rapid Support Forces [RSF] have been battling in the capital Khartoum and other areas of Sudan in a power struggle that exploded in mid-April.

More than three million people have been uprooted, including more than 700,000 who have fled to neighbouring countries.

UN Secretary General Antonio Guterres said last week that Sudan, Africa's third largest country by land area, was on the brink of full-scale civil war that could destabilise the wider region.

In El Geneina, witnesses have reported waves of attacks by local militias and the RSF against the non-Arab Masalit people, the largest community in the city, that have sent tens of thousands of people fleeing to nearby Chad.

While the ICC cannot currently work in Sudan due to the security situation, it intends to do so as soon as possible, the report said.

Under a 2005 UN Security Council resolution, its jurisdiction is limited to the Darfur region.