Earlier on Thursday security forces fired tear gas to disperse dozens of students demonstrating against the ruling military council at a financial academy in the heart of Sudan's capital Khartoum.
Dozens of lawyers had also gathered outside the main courthouse complex in Omdurman, Khartoum's twin city, calling for civilian rule and for people to join Sunday's planned demo, Presstv Reported.
Demonstrations in Khartoum have become rare since security forces broke up a sit-in outside the Defence Ministry on June 3, leaving more than 100 people dead, according to medical sources.
Protesters in Omdurman seemed upbeat as they marched on Thursday, playing music and waving Sudanese flags as one protester said that the violent end to the sit-in had "increased the people's fervour".
The sit-in had become the focal point of protests against former president Omar al-Bashir and the military council that ousted him on April 11.
Its dispersal caused the collapse of stalled talks between the military council and a coalition of opposition and protest groups over how to manage a transition towards elections.