The fighting that has erupted in the Sudanese capital, Khartoum, and elsewhere in the country is a direct result of a vicious power struggle within the country's military leadership.
There are clashes at key strategic places across the capital as members of a paramilitary force - Rapid Support Forces (RSF) - and regular soldiers fight.
Here is what you need to know.
Since a coup in October 2021, Sudan has been run by a council of generals and there are two military men at the centre of the dispute.
Gen Abdel Fattah al-Burhan, who is the head of the armed forces and in effect the country's president.
And his deputy and leader of the RSF, Gen Mohamed Hamdan Dagalo, better known as Hemedti.
They have disagreed on the direction the country is going in and the proposed move towards civilian rule.
One of the main sticking points is over the plans to include the 100,000-strong RSF into the army and who would then lead the new force.
The violence follows days of tension as members of the RSF were redeployed around the country in a move that the army saw as a threat.
There had been some hope that talks could resolve the situation but these never happened.
It is not clear who fired the first shot on Saturday morning but there are fears that this will worsen an already unstable situation.
Diplomats have urged the two sides to cease fire.
The RSF was formed in 2013 and has its origins in the notorious Janjaweed militia that brutally fought off rebels in Darfur.
Since then, Gen Dagalo has built a powerful force that has intervened in conflicts in Yemen and Libya and controls some of Sudan's gold mines.
It has also been accused of human rights abuses, including the massacre of more than 120 protesters in June 2019.
Such a strong force outside the army has been seen as a source of instability in the country.
This fighting is the latest episode in bouts of tension that followed the ousting of long-serving President Omar al-Bashir in 2019.
There were huge street protests calling for an end to his near-three decade rule and the army mounted a coup to get rid of him.
But the civilians continued to demand a role in the plan to move towards democratic rule.
A joint military-civilian government was then established but that was overthrown in another coup in October 2021.
And since then the rivalry between Gen Burhan and Gen Dagalo has intensified.
A framework deal to put power back in the hands of civilians was agreed last December but talks to finalise the details have failed.
If the fighting continues then it could further fragment the country and worsen political turbulence.
Diplomats, who have played a crucial role in trying to urge a return to civilian rule, will be desperate to find a way to get the two generals to talk.
In the meantime, it will be the ordinary Sudanese who will have to live through yet another period of uncertainty.
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