Jebril Abd Allah, an official in North Darfur State, was quoted by the Al-Sahafa newspaper as saying the releases took place on Monday.
He added the SLM promised to free the rest of its prisoners, but without giving a number or date.
The government released 54 SLM members in early September under a ceasefire accord with the rebels, according to presidential affairs minister Al-Tayeb Ibrahim Muhammed Khair.
A six-week ceasefire deal was signed in Chad on 3 September, but the rebels have since repeatedly accused the government of violating the truce.
Abd Allah acknowledged 102 people had been killed in the Sayalah region of North Darfur since the accord was signed, but he did not identify who was responsible for the deaths.
The conflict has raged since February in western Sudan's Darfur states, where the SLM say they are fighting for an end to marginalisation and neglect of the large, impoverished region.
Abd Allah said the fighting had cost 3000 lives. It had also left 400,000 displaced, according to UN estimates.
The United Nations has announced the launch of a $23 million humanitarian aid initiative to promote peace in the semi-desert region near the Chad border.