If they are digging through from outside, you will need to put in an underground fence of galvanized wire at least a foot deep to keep them out. Eventually, you may need to do this under the entire perimeter fence.
If they have made their home there, you will need to decide on a control method--live trap, poison, etc.--and possibly consult a professional.

Get a ferret man to visit. Rabbits will just dig their way back out if you block the holes.After all, they dug them out in the first place!!

I agree with Volunteer, get the rabbits out / finished off, then you'll need to fence to keep them out, burying the bottom of the wire as deep as you can. As they can dig, you'll need to patrol the perimeter, blocking any holes that they start to dig. And I'd fill in / collapse the burrows after the ferret man's been so there are no bolt-holes handy if any rabbits get in.

Have you considered getting a terrier as a pet?