The shake-up at the top comes as Sudanese civilians protest against the army rulers who took control after toppling president Omar al Bashir.
Sudan's Defence Minister Awad Ibn Auf has stepped down as leader of the new Military Transitional Council, he said, a day after ousting President Omar al Bashir.
Lieutenant General Abdel Fattah Abdelrahman Burhan will be the new head of the transitional council, Ibn Auf said in a speech broadcast on state TV on Friday.
State television showed army general Abdel Fattah Burhan being sworn in, not long after Defence Minister Ibn Auf announced he was stepping down as transitional leader.
Ibn Auf said he took the decision to step down in order to preserve the unity of the armed forces.
The Sudanese group spearheading a nationwide protest movement described a decision by the head of a newly formed military council to step down on Friday as a "victory" for the people.
"The stepping down of General Awad Ibn Auf is a victory of the people's will," the Sudanese Professionals Association said.
Meanwhile, sixteen people were killed by "live ammunition", with 20 wounded in Khartoum during ongoing protests over the past two days, according to a statement on Friday by Sudan's police spokesman General Hashim Abdelrahim.
The new military rulers vowed earlier on Friday to open a dialogue with all political groups on forming a civilian government as protesters railed against their seizure of power after removing president Bashir.
But the military council warned it would tolerate no breaches of security after protesters defied a night-time curfew to keep up a sit-in demanding immediate civilian rule.
TRT World speaks with political analyst Muhammad Elamin.
The head of the council's political committee, Lieutenant General Omar Zain al Abideen, confirmed that Bashir who had ruled the country for 30 years and was one of Africa's longest-serving leaders remained in custody.
But he said the council would never extradite him, or any other Sudanese, despite a long-standing arrest warrant issued by the International Criminal Court (ICC) against Bashir on charges of genocide and war crimes.
The military council appealed for financial aid from regional peers to tackle a worsening economic crisis.
"We want your donations as we have some economic issues," Abideen, told Arab and African diplomats in a televised meeting, citing "a shortage of essential items like flour and fuel."
TRT World 's Arabella Munro reports.
Protesters ask army transfer power
Earlier, the main protest organising group rejected the transitional military council's promise to set up a civilian government and hand over power to an elected president within two years.
"Our demands are clear, just and legitimate, but the coupists [the regime's security committee] ... are not capable of creating change, and they do not have the safety and stability to stay in power," the Sudanese Professionals Association said in a statement.
"This is not to mention the peaceful demands of handing over power to a transitional civilian government as one of the conditions that needs to be implemented."
Protesters held mass demonstrations for four months demanding Bashir's overthrow, defying repeated deadly attempts to crush them by riot police and the feared intelligence services.
But when the ouster was finally announced on Thursday in an address to the nation by the defence minister, it was met not with joy but anger.
Protest leaders dismissed the transitional military council as the "same old faces" from the old regime, which had led the country into multiple conflicts and worsening poverty and social inequality.
Thursday's announcement meant "we have not achieved anything," said one protester who gave his name only as Adel.
"We will not stop our revolution. We are calling for the regime to step down, not only Bashir."
Analysts said that Bashir's overthrow in a palace coup made the transition to democracy in Sudan a more distant prospect.
"Ironically, the prospects for democratic transition may be more remote than when Bashir was in power as there's no centre of power with which to negotiate," said Alex de Waal, executive director of the World Peace Foundation at the Fletcher School of Law and Diplomacy at Tufts University.
"The power struggle within the security cabal that took power yesterday is just beginning. Bashir had kept their rivalries and ambitions in check; his removal brings in its wake an unregulated uncertainty."
Thousands defied a warning from the military council to respect the night-time curfew imposed from 2000 GMT (10 pm) to 0200 GMT (4 am), to maintain their vigil outside army headquarters in Khartoum for a sixth straight night.
Protesters were seen chatting with soldiers posted outside. They said their quarrel was with the commanders who had led the coup, not the rank and file.
"There was no difference between last night and previous days and nights for us," said one protester who gave his name as Abu Obeida.
"This is now our square. We have taken it and won’t leave until victory is achieved.
"We broke the curfew. We will continue doing it until we have a civilian transitional government."
Military defends ouster
The Sudanese army claims it has no ambition to hold the reins of power, saying it responded to calls from the people against Bashir's rule.
Abideen told a press conference on Friday that the military wants to “guide the country forward” and act as a “tool for change.”
Abideen tried to strike a conciliatory tone, saying, “We came for you.”
Sudan's last elected prime minister, opposition Umma party leader, Sadiq al Mahdi, who was overthrown by Bashir in a military coup in 1989, was expected to address supporters after prayers at one of Omdurman's most revered mosques.
Since returning to Khartoum from self-imposed exile, Mahdi has allied his party with the grass-roots momentum driving the mass protests that preceded Thursday's coup.
Calls for restraint
Washington called on the military council "to exercise restraint and to allow space for civilian participation within the government."
The European Union urged the army to carry out a "swift" handover to civilian rule.
UN chief Antonio Guterres called for a transition that would meet the "democratic aspirations" of the Sudanese people and appealed for "calm and utmost restraint by all," his spokesman said.
That came after the African Union decried Bashir's military overthrow, saying it was "not the appropriate response to the challenges facing Sudan and the aspirations of its people."
The military council said it was declaring a ceasefire across the country, including in war-torn Darfur.
But the rebel Sudan Liberation Army (SLA-AW) fighting government forces in Darfur denounced what it called a "palace coup."
Sudan's feared National Intelligence and Security Service (NISS) said it was freeing all the country's political prisoners, state media reported.
But in the eastern cities of Kasala and Port Sudan, the releases failed to materialise, prompting protesters to storm NISS buildings, according to witnesses.