On the other is paramilitary group the Rapid Support Forces (RSF), the partner-turned-rival of the military.
The RSF is led by general Mohamed Hamdan Dagalo, better known as Hemedti. He is the deputy head of Sudan’s ruling Sovereign Council.
The two sides came together to oust former leader Omar al-Bashir in 2019 but there have been long-running disagreements over how the country should be run.
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‘Tension had been boiling’ in Sudan
Where is the fighting happening?
The fighting began at a military base south of the capital Khartoum, with both sides accusing the other of initiating attacks.
Clashes then spread across the city, including around the military’s headquarters, the airport and the presidential palace.
Witnesses have reported gunfire in many parts of the country, including heavy exchanges of gunfire in the northern city of Merowe and clashes in the Darfur cities of El Fasher and Nyala.
Who are the RSF?
The RSF is made up of about 100,000 troops and evolved from so-called janjaweed militias that fought in the Darfur conflict in the 2000s.
The RSF has long been accused of atrocities linked to the Darfur conflict.
In 2017, a law legitimising the RSF as an independent security force was passed.
Transition to democracy
Former president Omar al-Bashir was ousted in 2019 following months of protests against his three-decade authoritarian rule.