Six refugees from Sudan's strife-scarred Darfur region were killed and 10 others wounded in a brawl at the Bredjing camp in eastern Chad, a relief worker said on Friday.Food distribution was the cause of Wednesday's violence, said Abdel Hatim Tahir, coordinator with the Chad-based Agency for Economic and Social Development (ADES Internationale), an NGO active in the camp.The office of the UN High Commissioner for Refugees (UNHCR) confirmed the report.After almost 15 years of providing aid to refugees from Darfur, ADES and Chadian authorities launched an investigation "to understand the degree of socio-economic vulnerability among the refugees and to target those with the greatest need of food aid," said Simplice Kpandji, UNHCR spokesperson in Chad's capital N'Djamena.The inquiry, which covered some 320 000 refugees in Chadian camps, concluded that 55% were "extremely vulnerable", 31% were "vulnerable" and 14% were "autonomous", meaning that they could look after themselves."It was (decided) on the basis of these results that the distribution of food should exclude the category" of people held to be self-sustaining, Kpandji said.Some of these refugees, especially in the Bredjing camp, furiously rejected the decision to stop food aid."The refugees in the morning (on Wednesday) assaulted the members of their food distribution committee ... with knives and clubs," Tahir said.Chadian security forces intervened and placed "the perpetrators of the killing" under arrest and at the disposal of judicial authorities, the UNHCR said.In September, the United Nations estimated that 335 392 Sudanese refugees live in Chad. They have fled Darfur since the outbreak of conflict and a genocide there in 2003 and have mostly sought shelter in territory close to the border.In 2017, Sudan, Chad and the UN signed a tripartite agreement to enable the voluntary repatriation of Sudanese refugees living in Chad and vice versa.To date, only a few hundred Sudanese refugees and a few thousand Chadian refugees have returned to their homelands under the accord.Chad, a vast country extending south from North Africa deep into the heart of the continent, has also taken in almost 100 000 refugees from the Central African Republic, along with more than 10 000 Nigerians who fled conflict in the Lake Chad region.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook.