Yes, this is an African club. As you guessed probably from Kenya or Tansania. These are called 'RUNGU'. They are used by the Masai and adjacent tribes.
I don't think these clubs were used to throw. But...at wish, one can throw any club.
The shape of your club is peculiar. I guess they just dug out a root and followed its shape when making this piece. Perhaps the maker/owner liked this form.
Normally the head of a rungu is bent. In your case it has an S-shaped form.
I have a straight one in my collection. Length : 59 cm. Look at the pics