South Sudan fighting has 'greatly diminished': UN envoy

Fighting in South Sudan "has diminished greatly" since September's peace agreement between President Salva Kiir and former rebel leader Riek Machar, the UN's envoy to the African nation said on Tuesday.

Speaking in South Sudan's capital of Juba, David Shearer told reporters that he is encouraged by "a number of positive things" - opposition members once at war now in the capital Juba participating in the peace process, more than 15 "peace meetings" across the country, and civilians in UN protected sites starting to return home.

On the less positive side, Shearer said the UN peacekeeping mission he heads is concerned "that the momentum of the peace agreement and the peace talks might slow".

South Sudan plunged into ethnic violence in December 2013 and the five-year civil war has killed almost 400,000 people.

The conflict has also uprooted a third of the country's population, forcing nearly two-and-a-half million into exile as refugees and triggered several deadly famine.