spatially constrained clustering

Hi List,
         does anyone know of an implementation of spatially constrained 
clustering in R?

This is where there is a vector of measurements for points on a plane 
and only neighbors can be clustered together. I have tried implementint 
in myself -- but if someone has alkready done it !

I have searched on the obvios terms "spatially constrained clustering" 
without any luck.


Bye
Rob