  A set of exact quasi-local conservation equations is derived from the
Einstein's equations using the first-order Kaluza-Klein formalism of general
relativity in the (2,2)-splitting of 4-dimensional spacetime. These equations
are interpreted as quasi-local energy, momentum, and angular momentum
conservation equations. In the asymptotic region of asymptotically flat
spacetimes, it is shown that the quasi-local energy and energy-flux integral
reduce to the Bondi energy and energy-flux, respectively. In spherically
symmetric spacetimes, the quasi-local energy becomes the Misner-Sharp energy.
Moreover, on the event horizon of a general dynamical black hole, the
quasi-local energy conservation equation coincides with the conservation
equation studied by Thorne {\it et al}. We discuss the remaining quasi-local
conservation equations briefly.
