Commonly when Africans learn English they are taught that tribe is the term that English-speakers will recognize. Take the word isizwe in Zulu. Often Zulu-speakers will use the English word tribe because that's what they think English speakers expect, or what they were taught in school. Yet Zulu linguists say that a better translation of isizwe is nation or people. When Africans use the word tribe in general conversation, they do not mean the negative connotations of primitivism the word has in Western countries.
African leaders see tribalism as a major problem in their countries.
This is true. But what they mean by this is ethnic divisiveness, as intensified by colonial divide and rule tactics. Colonial governments told Africans they came in tribes, and rewarded people who acted in terms of ethnic competition. Thus for leaders trying to build multi-ethnic nations, tribalism is an outlook of pursuing political advantage through ethnic discrimination and chauvinism. African ethnic divisions are quite real, but have little to do with ancient or primitive forms of identity or conflict.