Gunmen shot and seriously wounded three aid workers in an attack on a humanitarian convoy in the Darfur region of western Sudan, the UN said in a statement.
The United Nations said the two vehicles with eight people on board working for World Vision International (WVI), a non-governmental organisation, was ambushed on Thursday near Bulbul Timisgo, a small village in South Darfur State.
"Two WVI staff were shot in the head, and a third in the arm. The remaining staff suffered minor injuries caused by glass fragments and shrapnel," the statement added. "The vehicles were clearly marked as humanitarian transport."
"This is a horrifying and brutal attack on aid staff who are working to save the lives of Sudanese people," the statement said, quoting John Holmes, the UN Under-Secretary-General for Humanitarian Affairs and Emergency Relief Coordinator.
The UN did not say who it believed was behind the attack. But it said the same has seen banditry and clashes between rival Arab tribes during 2007.
The UN said attacks on relief workers in Darfur increased 50 per cent between June 2006 and June 2007.
Since the beginning of the year 98 vehicles belonging to humanitarian staff have been hijacked, 105 staff temporarily taken hostage, more than 66 humanitarian personnel physically or sexually assaulted and 61 convoys ambushed and looted, it said.
Violence has increased in Darfur since 2006, when only one of three negotiating rebel factions signed a peace deal that was rejected by the majority of Darfuris.
International experts say some 200,000 people have died in Darfur as a direct or indirect result of four and a half years of conflict between mainly African rebels and the government and its Arab militia allies. Khartoum says 9,000 people have died.
The UN and African Union and representatives from 26 countries met in New York yesterday to try to expedite the deployment of a joint UN-AU peacekeeping force of 26,000.