Egypt has denied allegations that its air forces bombed rebels in South Sudan's Upper Nile state. Rebel forces from the Sudan People's Liberation Army-In Opposition (SPLA-IO) claimed Cairo had carried out "more than nine bombs and explosions" in the country's rebel-held areas at the weekend.
SPLA-IO also claimed that Egypt's alleged involvement signalled the South Sudanese government's intention to provoke a regional war.
However, Ahmed Abu Zeid, spokesperson for Egypt's foreign ministry, denied the allegations and said Cairo does not intervene in internal affairs of other countries.
South Sudan's presidency also slammed the allegations as "nonsense".
"Those small pockets of rebels are... operating inside our population and we cannot bomb our own population," spokesperson Ateny Wek Ateny said, according to Reuters.
South Sudan descended into war in 2013 – just two years after gaining independence from Sudan – when President Salva Kiir, of the Dinka ethnic group, fired his deputy and rebel leader Riek Machar from his cabinet.
Kiir and Machar have agreed on several peace deals – the last of which was signed in August 2015 – but have failed to control their troops, who have broken every ceasefire since 2014.
Ethnic-related violence targeting Dinka and Nuer has killed an estimated 50,000 people, amid allegations of crimes against humanity committed by both sides, including rape, torture and the use of child soldiers. Millions are displaced and are facing severe food shortages due to a man-made famine.
Machar fled South Sudan following deadly fighting in capital Juba in July 2016.
Clashes have now reached Malakal, once one of South Sudan's largest urban areas and now a "largely deserted" area, according to the United Nations. The town is now home to more than 33,000 internally displaced persons (IDPs).
Earlier this month, International Organization for Migration (IOM) warned renewed violence in war-was hindering humanitarian assistance to thousands of people displaced by the conflict.