Sudan's army reportedly suspended participation in Saudi Arabia-hosted cease-fire talks with the Rapid Support Forces (RSF) paramilitary group.
The news was carried by a number of Sudanese media outlets, including Aljareeda newspaper and the Alrakoba news portal.
There was no confirmation yet from the Sudanese army.
The reports emerged as fierce clashes erupted late Tuesday between the army and RSF fighters in the capital Khartoum and El-Obeid city, the capital of North Kordofan state.
A 7-day cease-fire brokered by Saudi Arabia and the U.S. between the two sides expired on Monday. The conflicting rivals agreed to extend the agreement for five more days.
At least 863 civilians have been killed and thousands injured in clashes between the army and the RSF since April 15, according to local medics.
The International Organization for Migration (IOM) estimates that more than one million people have been internally displaced by the conflict.
A disagreement had been fomenting in recent months between the army and the RSF over the paramilitary group's integration into the armed forces, a key condition of Sudan's transition agreement with political groups.
Sudan has been without a functioning government since October 2021 when the military dismissed Prime Minister Abdalla Hamdok's transitional government and declared a state of emergency in a move decried by political forces as a "coup."
Sudan's transitional period, which started in August 2019 after the ouster of President Omar al-Bashir, had been scheduled to end with elections in early 2024.