The United Nations Office for Coordination of Humanitarian Affairs says 13 humanitarian aid workers have been killed in South Sudan since the conflict began in December last year.

In its monthly humanitarian report, UN OCHA says the majority of the humanitarian aid workers who have been killed are South Sudanese nationals.

Six of them were killed just two weeks ago, in Maban County of Upper Nile State.

The Humanitarian Coordinator in South Sudan, Toby Lanzer, told the UK-based Guardian Newspaper, that the best way to honour the work of humanitarians in South Sudan is to work for peace.

He said there is need for an immediate end to all violence against civilians so that aid workers are able to do their life-saving work in safety.

Mr. Lanzer calls the attacks on aid workers symptomatic of the brutal violence against civilians that he says has characterised the conflict in South Sudan.

The UN Official said the parties to the conflict must be held accountable for keeping people safe from harm, and for participating meaningfully in the peace process to end the conflict.