Dapa Arnaud gives a list of the 10 most active african presidents [fr] on social media. At the top of the list is  president Paul Kagame in Rwanda:

In place since 2003, the president of Rwanda is the most active on the internet.  According to the Ecofin agency, Paul Kagame interacts with many users on Twitter through his account @PaulKagame. His personal website named “The Journey Continues, Dukomeze Imihigo” is also one of the most visited websites in the country. His presence is also quite strong on other social media sites such as Facebook, Google+, Flickr or YouTube.