Stephane Dujarric, a UN spokesman said on Monday: "The Sudanese Government decided, effective today, to reverse its decision to suspend UN Mission in Sudan (UNMIS) activities in Darfur."
The United Nations coordinates one of the world's largest aid operations in Darfur and monitors the health, malnutrition and human rights situation in a region the size of France.
Sudan suspended the UN operations, excluding the work of the World Food Programme and the UN Children's Fund, because it said the world body used a helicopter to move Suleiman Adam Jamous, a rebel leader who opposes a recent peace deal.
Dujarric said that Taye Zerihoiun, the deputy special UN envoy for Sudan, had told Mutrif Siddiq, the Sudanese undersecretary for foreign affairs, that the mission was investigating the incident.
Dujarric and other UN spokesmen declined to comment on whether the United Nations had moved Jamous in a helicopter.
Jamous was the humanitarian coordinator for the main rebel Sudan Liberation Army (SLA) before it split in November last year. He was the main contact for the more than 14,000 aid workers in the region.