  We present a measurement of form-factor independent angular observables in
the decay \mbox{$B^0\to K^{*}(892)^{0}\mu^+ \mu^-$}. The analysis is based on a
data sample corresponding to an integrated luminosity of 1.0fb$^{-1}$,
collected by the LHCb experiment in $pp$ collisions at a center-of-mass energy
of 7TeV. Four observables are measured in six bins of the dimuon invariant mass
squared, $q^2$, in the range $0.1<q^2<19.0$GeV$^{2}$/c$^{4}$. Agreement with
Standard Model predictions is found for 23 of the 24 measurements. A local
discrepancy, corresponding to $3.7$ Gaussian standard deviations, is observed
in one $q^2$ bin for one of the observables. Considering the 24 measurements as
independent, the probability to observe such a discrepancy, or larger, in one
is $0.5\%$.
