Some protesters and eyewitnesses reported that security forces had fired live rounds at them in the Burri neighborhood of Khartoum, and videos posted on social media by local activists appear to show at least one man being treated for a head injury. Gunshots can be heard in other footage in which the Burri Almahas Mosque is seen in the background.

The near-daily demonstrations initially began over corruption and mismanagement of the economy.

But as the unrest broadened over the past month, so did the message of the protesters, who turned their focus to the overall leadership of Mr. Bashir, who has ruled Sudan since 1989, when he seized power in a coup. His party has moved to change the country’s Constitution to prolong his rule.

On Thursday, security forces were deployed in large numbers in the capital.

The Sudan Doctors Committee issued a statement accusing the security services of preventing ambulances and emergency responders from reaching those wounded in Thursday’s demonstrations. It demanded immediate access to “every citizen who needs medical assistance.”

Human rights groups have urged the Sudanese government to end what they said was unwarranted use of force against protesters and to enact reforms that have long been called for by the international community.