Friends not deleting?

Ok, I have a lot of friends on my friends list that I have totally no clue who they are and I want to get rid of them.
I go to the top right of the screen to the buddy tab and delete them all. Enter a game and look back on my friends list and they are there again...So I right click on their names and press 'Remove Friend' and they are gone, the I enter a game, finish it and they are back on it.......
Whats happening? -.-