He said two cells have been established in Khartoum and the main southern town of Rumbek to follow up implementation of the repatriation provisions and to compile information about the refugees.
The January peace deal for southern Sudan ended 21 years of fighting in south Sudan that had claimed at least 1.5 million lives and displaced four million people.
In addition to the refugees from the south, almost 4,000 displaced persons from the Nuba mountains, an area the size of Austria where a separate truce was signed in January 2002, have also returned to their homes, Umdah said.
Before the 2002 truce, fighting raged in the Nuba Mountains, for more than two decades. Although geographically in the north of the country, its inhabitants fought alongside the southern rebel SPLM/A.