Sudan's sovereign council head General Abdel Fattah al-Burhan issued a decree on Friday sacking Rapid Support Forces (RSF) leader General Mohamed Hamdan Dagalo, widely known as Hemedti, from his position as deputy of the council with immediate effect.
Burhan also appointed former rebel leader Malik Agar as a deputy on the council.
The army and the RSF have been locked in weeks of conflict that has killed hundreds of people and turned the streets of the capital Khartoum into war zones.
More than a million people have been displaced by fighting in Sudan so far, including a quarter of a million refugees, a UN Refugee Agency (UNHCR) spokesperson said on Friday.
The latest figure includes some 843,000 people displaced internally and around 250,000 people who have fled across Sudan's borders, UN refugee agency spokesperson Matthew Saltmarsh told a Geneva briefing.
Refugees have streamed into Sudan's neighbors, including Chad, Ethiopia and South Sudan, with their own poorly-funded humanitarian crises. Egypt has so far received the highest number of Sudanese refugees with around 110,000 arriving there since the conflict broke out last month, Saltmarsh added.
"Many of those who have approached us are in a distressed state having been exposed to violence or traumatic conditions in Sudan, and having suffered arduous journeys," Saltmarsh said. The pace has increased in recent weeks, he added, with some 5,000 arriving each day in Egypt.