As the three-day ceasefire between the Sudanese Army and the Rapid Support Forces (RSF) expired, the RSF set fire to the intelligence building next door to Army Headquarters.
According to media reports, the renewed violence in Khartoum comes as the aid organisation, Doctors Without Borders reported severe violence against civilians in the West Darfur region.
People trying to flee to neighboring Chad were shot at and killed, according to the report.
There have been repeated attacks in Sudan even during the ceasefire.
As in previous ceasefires, the Army and the RSF accused each other of breaking the agreement brokered with the help of Saudi Arabia and the United States.
Since mid-April, there have been several ceasefires, but they have never been observed.
According to the United Nations International Organisation for Migration (IOM), almost 2.2 million people are on the run as a result of the conflict.
According to the World Health Organisation (WHO), almost 25 million people need help, including at least four million children