At least 18 people were killed and over 70 wounded in the clashes in the UN camp on Wednesday to Thursday in the north-eastern town of Malakal in South Sudan.

At least 18 people were killed and over 70 wounded in the clashes in the UN camp on Wednesday to Thursday in the north-eastern town of Malakal in South Sudan, Doctors Without Borders (MSF) has said, including two of their own staff killed. forty-six of the injured had bullet wounds.

Residents reported gunmen shooting in crowded areas in the tightly packed camp of tents and basic shelters housing over 47,700 people fleeing a civil war that began in late 2013.

The UN Mission in South Sudan (UNMISS) blamed the clashes on rival tribes inside the camp - "between Shilluk and Dinka youths" -- saying "at least seven" people were killed.

It added that "such an attack against civilians and UN premises may constitute a war crime."

Resident Jacob Nhial described government troops wearing the uniform of the Sudan People's Liberation Army (SPLA) "shooting at civilians" with fighting taking place in the camp, as well as gunfire coming from soldiers outside.

Confidential UN communication seen by AFP also said that SPLA soldiers took part in the attack.

"SPLA troops numbering 50-100 have entered the UNMISS POC Sector 1 and 2 in Malakal reportedly attacking IDPs, shooting sporadically, burning tents and looting properties," the internal UN document reads.

A POC, or Protection of Civilian site, is the UN acronym for places where South Sudan civilians are supposed to be safe, defended by peacekeepers while IDPs is the term the UN uses for internally displaced people.

An entire section of the camp was razed to the ground, with sporadic shooting still heard in Malakal on Friday morning, aid workers said.

The International Organization for Migration (IOM) said half the camp had fled their shelters -- some 25,000 people -- with areas, "looted and burned, including shelters, clinics and water tanks."

The UN mission has more than 12,000 peacekeepers with half of them deployed solely to protect the nearly 200,000 civilians sheltering in their bases around the country.

SPLA spokesman Marko Mayol said he had no information on the reports that government troops were involved.