The casualties were all protesters who had been demonstrating in the city of Kassala in support of the provincial governor, who was sacked earlier this week.
Seven people were shot dead and 30 others wounded during a demonstration in eastern Sudan, where tensions are high between rival groups, medics have said.
A doctors' committee said on Thursday all the dead and injured were protesters.
The governor of Kassala, who belongs to the Beni Amr tribe, was sacked on Tuesday by Prime Minister Abdalla Hamdok.
His dismissal had also sparked demonstrations in Port Sudan and nearby Suakin on Wednesday, when medics said six people were killed and 20 wounded.
Following the unrest, authorities extended an overnight curfew that had been imposed on Wednesday night in the Red Sea port cities.
Witnesses said protesters had blocked streets in the two cities during Wednesday's demonstrations.
A regional doctors' committee said, "The victims were attacked with knives and swords."
The appointment in July of Saleh Ammar as governor of the eastern state of Kassala had aroused the anger of the Beja, the other major tribe in the region.
At the end of August, three people died and another dozen were wounded in clashes following the appointment. Since then, tensions have been high.
Last week, members of the Beja tribe blocked the docks in Port Sudan, the country's economic lifeline.
They were protesting against a peace agreement signed October 3 in Juba between rebel groups and the government, that includes a section on the eastern region.
The Beja fear their tribe will be under-represented in regional legislative and executive bodies under the Juba agreement, to the benefit of the Beni Amr.
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