Executive director of the UN's World Food Programme, Cindy McCain, has indicated that she is "appalled and heartbroken" by the murder of three workers in the Darfur region of Sudan.

In a statement, she says two other WFP employees were injured in the same incident.

"We have informed the families of these dedicated team members and stand with them and our entire WFP family at this time of catastrophe," she says.

"Any loss of life in humanitarian service is unacceptable and I demand immediate steps to guarantee the safety of those who remain."

Aid workers are neutral and should never be a target. Threats to our teams make it impossible to operate safely and effectively in the country and carry out WFP’s critical work.Cindy McCainWFP Executive Director