International film star and Goodwill Ambassador for the United Nations refugee agency Angelina Jolie has appealed for greater support for Afghan returnees, particularly as the harsh winter approaches, as she wrapped up her first visit to the strife-torn nation.

The top United Nations envoy to Afghanistan has condemned recent attacks against civilians in the violence-wracked nation, including a suicide bombing on Monday that killed five children in Kunduz, the murder of a number of passengers on a bus in Kandahar and the killing of a foreign aid worker in the capital, Kabul.

United Nations agencies are helping authorities to respond to a diarrhoea outbreak in Afghanistan, where only about a quarter of the population has access to safe drinking water and 20 per cent of child deaths is attributed to the easily preventable disease.