Sustained firing broke out in the Sudanese capital Saturday morning amid simmering tensions between the army and the paramilitary Rapid Support Forces (RSF).
The sounds of heavy shooting could be heard in a number of areas, including central Khartoum and the neighbourhood of Bahri.
An Asharq Al-Awsat correspondent said that heavy gunfire could be heard in the eastern side of the army's headquarters, near Khartoum International Airport.
In a statement issued Saturday morning, the RSF accused the army of attacking its forces at one of its bases in South Khartoum. The military used light and heavy weapons in the attack, it said.
Also, a Reuters witness saw cannon and armoured vehicles deployed in streets, and heard the sound of heavy weaponry in the vicinity of the headquarters of both the army and RSF.
The source of the gunfire could not be immediately confirmed by Reuters. People could be seen running in a state of panic in Khartoum.
The rift between the forces came to the surface on Thursday, when the army said that recent movements by the RSF had happened without coordination and were illegal.
A statement by the RSF on Saturday called the army's actions a "brute assault" and called for it to be condemned.
It said that the RSF had been in contact with local and international mediators to inform them.
A confrontation between the two forces could spell prolonged strife across a vast country already dealing with economic breakdown and flare-ups of tribal violence.
The move follows days of tension between the army and the RSF, a powerful paramilitary group, that had sparked concern about a confrontation.