Sudan's President Omar al-Bashir has ordered the disarmament of all militias in Darfur, where more than 10,000 people have died in recent fighting.
The pro-government Janjaweed were mentioned by Bashir
The decree specifically calls for the disarming of the Janjaweed, the Arab militia blamed for perpetrating atrocities against African farmers.
There has been strong criticism of Sudan for failing to curb the militias.
The US has threatened sanctions against Sudan, unless what Washington describes as ethnic cleansing is ended.
A statement released by the presidency said government bodies should act "to control and pursue all outlaw groups, including rebels and Janjaweed".
It also called officials to prevent any groups from crossing into neighbouring Chad.
On Friday, Chad said it had killed 69 Sudanese Janjaweed militia men on its territory.
African Union head Alpha Omar Konare will travel to Darfur in western Sudan on Sunday to review the work of African ceasefire monitors, who are due to be fully operational this weekend.
The Darfur conflict erupted a year ago, and has been described by the UN as the worst humanitarian situation in the world.
The Janjaweed have been accused of mass killings and extensive human rights abuses.
Sudanese officials have said in the past it would be hard to disarm the Arab militias while the two main rebel groups - the Sudan Liberation Movement and the Justice and Equality Movement - were operating in the region.