How do I stop my 2.5yo pushing and hitting?

One of the nursery staff keeps commenting that my 2.5yo is pushing and shoving the other kids.

My kid is now very verbal and quite able to express his feelings, and he shows genuine concern when other children cry. So odds are good.

On kindergarten recommendation we've now been reading books about being a good friend and we remind him that pushing is not nice and that good friends do not push or hit each other. But the message doesn't get through.

How did you get your toddler to stop pushing and hitting?

I haven't seen it in action. but my toddler has confessed that he has pushed his friend and that the friend feel over and started crying.