The 176 PoWs freed by the Sudan People's Liberation Movement (SPLM) on Tuesday include four officers who were held for five years in eastern Sudan.
The soldiers were handed over to the Sudanese Armed Forces in the presence of representatives from the International Committee of the Red Cross, Aljazeera reported.
They represent the first batch of prisoners to be released, the SPLM said, but declined to reveal the number of those still to be freed.
The SPLM signed a peace deal with the Sudanese government in January to end 21 years of fighting in the south of the country.
The SPLM has freed hundreds of government soldiers since then, but this was the first time the movement released those captured in battles in eastern Sudan.
The official Sudan News Agency said the soldiers would be hosted at locations in the capital before being allowed to travel to their hometowns to resume normal life.
The SPLM, which joined its former foes in a government of national unity in September, has not revealed the number of government soldiers it is still holding.
Khartoum says it does not have any rebel prisoners of war.