Railway workers and other protesters are gathering in Atbara, the northern transport hub where the uprising began in December, and will travel by train to the capital, Khartoum, AP reported.
The call by the Sudanese Professionals Association comes amid heightened tensions with the military council that seized power earlier this month. The protesters have called for an immediate move to civilian rule and say they will announce their own transitional council on Thursday.
The SPA has also vowed to maintain a mass sit-in outside the military headquarters in Khartoum, after the military called for the reopening of roads and the removal of barricades.