The Sudanese army has warned that the country's biggest paramilitary group is mobilising troops in cities across the country.
In a statement released in the early hours of Thursday, the military accused the Rapid Support Forces (RSF) of clearly breaking the law.
There are growing fears of a confrontation between the two sides.
The RSF leader, Mohamed Hamdan "Hemeti" Dagolo, played a key role when the army seized power in Sudan in 2021.
This week leaders failed to meet a deadline to form a civilian-led government.
The breakdown of the talks has been blamed on differences between rival military factions.