  We study the influence of magnetised crusts on torsional shear mode
oscillations of magnetars. In this context, we employ magnetised crusts whose
ground state properties are affected by Landau quantisation of electrons. The
shear modulus of magnetised crusts is enhanced in strong magnetic fields $\geq
10^{17}$ G. Though we do not find any appreciable change in frequencies of
fundamental torsional shear modes, frequencies of first overtones are
significantly affected in strong magnetic fields. Furthermore, frequencies of
torsional shear modes calculated with magnetised crusts are in good agreement
with frequencies of observed quasi-periodic oscillations.
