Chad may face genocide, UN warns (BBC)

From the BBC: Chad may face genocide, UN warns 16 Feb 2007:

Eastern Chad and Darfur have a similar ethnic make-up, with nomadic Arab groups and black African farmers both seeking access to land and scarce water points.

Our reporter says the violence in Chad follows the same pattern as in Darfur - mostly Arabs on camels and horseback attacking non-Arab villages.

I wonder how the reporter can tell who is Arab or non-Arab.