  A sufficiently long lived warm dark matter could be a source of X-rays
observed by satellite based X-ray telescopes. We consider axinos and gravitinos
with masses between 1 keV and 100 keV in supersymmetric models with small
R-parity violation. We show that axino dark matter receives significant
constraints from X-ray observations of Chandra and SPI, especially for the
lower end of the allowed range of the axino decay constant $f_{a}$, while the
gravitino dark matter remains unconstrained.
