South Sudan rebels accused Egypt on Saturday of carrying out bombing raids against their positions, drawing an immediate denial from Cairo, and warned of the risk of a regional war.
It was the first time either side had alleged Egyptian involvement in South Sudan's festering conflict, which pits President Salva Kiir's military against forces loyal to his former vice president, Riek Machar.
The Egyptian air force on Friday dropped "more than nine bombs and explosions on the gallant SPLA-IO positions" near the northern village of Kaka, a rebel statement said, using an acronym for the rebel force.
Egyptian foreign ministry spokesman Ahmed Abu Zeid denied the alleged air strikes, saying: "Egypt does not interfere in the internal affairs of other countries."
South Sudan presidential spokesman Ateny Wek Ateny also denied Egypt had conducted any bombings in the country, describing the allegations as "nonsense."
"Those small packets of rebels are ... operating inside our population and we cannot bomb our own population," he said.
War erupted in South Sudan in December 2013 after a political disagreement between Kiir and Machar exploded into military confrontation.
Under a peace deal, Machar returned to the capital Juba as vice president early last year. But tensions escalated between the two men, who hail from rival tribes, and fighting broke out again in Juba in July.
Intermittent clashes continue in several parts of the country. The conflict has often taken an ethnic hue, fuelling fears the world's youngest nation could be plunged into a genocide on the scale of Rwanda's in 1994.
In the statement, the rebels accused Kiir's government of seeking to escalate the war. They said they repelled attacks by government forces in several places this week, including at three locations in Unity State, leaving "so many dead bodies".
The statement said the rebels had captured nine soldiers after firefights, and destroyed four military vehicles.
"Egyptian participation in the ongoing war in South Sudan are clear indications to the people of South Sudan...that the Juba regime is provoking the region and tilting South Sudan for a regional war," the statement said