The rights group pressed Sudanese President Omar al-Bashir act on commitments made April 1 to free political prisoners. Human Rights Watch said at least 100 political prisoners remain detained, though 24 have been released.
The rights group joined the Human Rights and Development Organization and the African Center for Justice and Peace Studies in calling on the Sudanese government to let independent monitors oversee the release of the remaining prisoners.
"Sudan should also urgently reform its repressive national security laws in line with international standards," Director of African programs at Human Rights Watch Daniel Bekele said in a statement from Nairobi.
Rights organizations say many of those who remain in prison are from Blue Nile and South Kordofan states in Sudan.
The U.S. State Department last week issued an alert to U.S. citizens warning of the risks present in South Kordofan and Darfur regions of Sudan.
Amnesty International said it interviewed internally displaced people from South Kordofan. They said villages were attacked by the Sudanese military from June to December, though there were no military or rebel targets in the area.