Renewed fighting broke out last week in the states of South Kordofan and Blue Nile between the army and a faction of the Sudan People's Liberation Movement-North (SPLM-N) led by Abdel Aziz al-Hilu.

United Nations resident and humanitarian coordinator in Sudan Clementine Nkweta-Salami said the fighting had reportedly claimed at least 80 lives in South Kordofan state capital Kadugli alone.

"I condemn the reported use of women and children as human shields in Kadugli, the obstruction of humanitarian aid, and the detention of civilians including children," the UN's most senior official in the country said in a statement.

Sudan's army and its main rival, the paramilitary Rapid Support Forces, have been at war for control of the country since April 2023, creating a widespread humanitarian crisis.

Hilu's unaffiliated faction of the SPLM-N has clashed with both since the war broke out.

In recent days, the army and the SPLM-N have accused each other of launching attacks and targeting civilians in an attempt to capture territory.

The UN warned the escalating violence would only worsen the already dire humanitarian situation, with millions cut off from life-saving aid.

"The consequences of food insecurity are already being felt in parts of South Kordofan, where families are surviving on dangerously limited food supplies, and malnutrition rates are rising sharply," Thursday's statement said.

Around half a million people are currently on the brink of famine in South Kordofan and Blue Nile, according to the Integrated Food Security Phase Classification.

The UN-backed assessment has already declared famine in parts of the Nuba Mountains, where SPLM-N maintains a foothold.

Across the country, fighting since April 2023 has killed tens of thousands, uprooted 12 million and pushed nearly 26 million people into acute food insecurity.