I think you will find if you're flying your own a/c through these places and it is on a permit to fly rather than c of a you will need permission from each country. On a C of A I believe it's a different matter.
Permissions I've obtained for flying in Africa i've used Paul Portnoi at Overflight to help. 01403 275835. He's a nice chap and very helpful.
Regards,
Jim.
www.microlightadventures.co.uk