"Black Hebrews"  claim to be Jews -- but they are not Jews. 
(The) Chief Rabbinate of Israel declared that the Black Hebrews were not Jews, and therefore the sect's members were not entitled to Israeli citizenship under the Law of Return. Nevertheless, the Black Hebrew population in Dimona continued to grow due to their high birthrate and because many of them, some with criminal backgrounds, illegally entered Israel using various forms of subterfuge. Jewish Virtual Library
There are black Jews -- such as the Jews from Lemba -- but this particular group is not Jewish although they have tried to claim they are the "only" Jews.  

סופי

And everything that Sarah tells you, listen to her voice. Bereshit (Genesis) 21:12