"Five martyrs succumbed to direct wounds from sniper bullets during a peaceful rally in Al-Obeid," the committee said in a statement.
The reason for the rally was not immediately clear but it came as protest leaders and the ruling generals prepare to resume talks in Khartoum on Tuesday.
The two sides are to meet to resolve remaining issues concerning the transfer of power from the ruling military council to a new civilian administration.
The generals and protest leaders agreed on July 17 to form a new joint civilian-military governing body that would install an overall civilian rule in the country.
That is the main demand of a nationwide protest movement that led to the April ouster of longtime leader Omar al-Bashir and has since demanded that the military council which took his place cede power to civilians.