South Sudan has decided to expel the United Nations' outspoken aid coordinator Toby Lanzer just weeks before he was to leave for a new assignment, UN officials said Monday.

UN Secretary-General Ban Ki-moon condemned the move and called on Juba to immediately reverse the decision targeting Lanzer, a British national who also served as UN deputy envoy to South Sudan.

Ban's spokesman announced the decision in a statement, noting that Lanzer was coming to the end of his term and that Eugene Owusu of Ghana had already been appointed to replace him.

No reason was given for the expulsion, but UN officials suggested that criticism directed at the government and the rebels over the recent upsurge of fighting may have angered Juba.

"Mr Lanzer has been instrumental in addressing the increasing humanitarian needs of conflict-affected communities in the country and ensuring that life-saving humanitarian assistance reaches the most vulnerable," the spokesman said in a statement.

Lanzer was not in South Sudan on Monday, but he was planning on returning to wrap up final business, a UN official said.

South Sudan is among the UN's worst humanitarian crises, with more than 2.5 million people facing severe food shortages.

The world's newest state was plunged into conflict nearly 18 months ago between forces loyal to President Salva Kiir and rebels allied with his former deputy, Riek Machar.

Lanzer has put the blame for the worsening violence squarely on the shoulders of the leaders who have signed several peace accords and failed to implement them.

- Outspoken envoy -

During the upsurge in violence last month in Unity and Upper Nile states, Lanzer released a statement expressing dismay after up to 100,000 people fled their homes in just one week.

"People should never be harmed, and certainly not targeted or forced to flee from their homes," he said.

After South Sudan's army advanced on the opposition-held town of Leer, Lanzer cited witnesses who gave disturbing accounts of rape and of the killing of civilians including children.

The military operations, he said, have "again devastated countless lives."

Active on social media, last week Lanzer tweeted: "4.6 million people in South Sudan will be severely, yes severely, food insecure by July. That is 800,000 more than in July of last year."

Lanzer is due to take up a new post as UN regional humanitarian coordinator for the Sahel at the end of June.

He has worked for the United Nations in several conflict zones including Sudan, the Central African Republic and East Timor.

The United Nations has repeatedly called on the two leaders to put an end to the fighting and put South Sudan back on the path to peace.

More than 120,000 people are sheltering in UN bases in South Sudan since the fighting broke out in December 2013.

The Security Council threatened in March to impose sanctions on those who obstruct peace and adopted a resolution that sets up a committee to begin work on the measures, but no action has been taken.
Source: AFP