If they are small shoots, just use a spade to dig down to them and cut them from the parent tree.

You need to identify this tree? So you can decide if its going to be an on going invasive problem? as you may need to enlist your neighbours help to control/contain it.

When I had this from my back neighbours Rhus some years ago I just killed off the shoots with some noxious spray substance with a plastic bottle over it. Some time later he removed the tree himself, as it was invading his tiny garden too!! It's amazing how far these shoots travel under a lawn and pop up everywhere.