  We present the analytic next-to-next-to-leading perturbative QCD corrections
in the leading twist approximation for the moments N=2,4,6,8 of the flavour
singlet deep inelastic structure functions F_2 and F_L. We calculate the
three-loop anomalous dimensions of the corresponding singlet operators and the
three-loop coefficient functions of the structure functions F_L and F_2. In
addition, we obtained the 10th moment for the non-singlet structure functions
in the same order of perturbative QCD. We perform an analysis of the obtained
results.
