The US ambassador to Sudan has been forced to take shelter after sustained fighting broke out in the capital Khartoum, as tension between the military and powerful paramilitary forces escalates.

John Godfrey said he and embassy staff were sheltering in place as heavy firing was heard in a number of areas.

The Rapid Support Forces militia claimed they had seized Khartoum airport and the presidential palace, as well as an airport and air base in the northern city of Marawi.

It accused the army of attacking its forces at one of its bases, while the Sudanese Army said the fighting broke out after RSF troops tried to attack its forces in the southern part of the capital.

In a statement, the military declared the RSF a “rebel force”, describing the paramilitary’s statements as “lies”.

Mr Godfrey said the escalation was “extremely dangerous” and called on senior leadership to stop the clashes.

The army said the RSF had tried to attack its troops in several places after witnesses reported heavy gunfire in multiple parts of the country, raising fears of a full-blown conflict.

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The clashes come as tensions between the military and the RSF have escalated in recent months, delaying the signing of a deal aimed at transitioning towards democratic elections.

Current tensions between the army and the paramilitary stem from a disagreement over how RSF should merge with the military – a process that is a key condition of the transition agreement.