  We consider self-dual Yang-Mills instantons in 4-dimensional Kaehler spaces
with one holomorphic isometry and show that they satisfy a generalization of
the Bogomol'nyi equation for magnetic monopoles on certain 3-dimensional
metrics. We then search for solutions of this equation in 3-dimensional metrics
foliated by 2-dimensional spheres, hyperboloids or planes in the case in which
the gauge group coincides with the isometry group of the metric (SO(3), SO(1,2)
and ISO(2), respectively). Using a generalized hedgehog ansatz the Bogomol'nyi
quations reduce to a simple differential equation in the radial variable which
admits a universal solution and, in some cases, a particular one, from which
one finally recovers instanton solutions in the original Kaehler space. We work
out completely a few explicit examples for some Kaehler spaces of interest.
