They probably slide onto a plate that is screwed to the wall. At least the ones we bought at Home Depot work that way.

First run a blade around each piece attached to the wall. It looks like they are caulked. Whether caulked or painted to the wall, the seal has to be cut. It will reduce the amount of damage to the wall.
As the prev writer noted, they may be fit onto a plate screwed to the wall.
When you cut the seal you will be better able to tell how it is attached to the wall. Does it have any give when u wiggle it. Go slow and try to figure this out. You may do damage to the wall and that is allright because it is repairable. Not difficult and not expensive.

Thank you so much Judarb, very appreciated. I will give it a try and let you know how it goes.