  We prove that spatial Kerr solitons, usually obtained in the frame of
nonlinear Schroedinger equation valid in the paraxial approximation, can be
found in a generalized form as exact solutions of Maxwell's equations. In
particular, they are shown to exist, both in the bright and dark version, as
linearly polarized exactly integrable one-dimensional solitons, and to reduce
to the standard paraxial form in the limit of small intensities. In the
two-dimensional case, they are shown to exist as azimuthally polarized
circularly symmetric dark solitons. Both one and two-dimensional dark solitons
exhibit a characteristic signature in that their asymptotic intensity cannot
exceed a threshold value in correspondence of which their width reaches a
minimum subwavelength value.
