  We study bosonic string theory in the light-cone gauge on AdS_3 spacetime
with zero radius of curvature (in string units) R/\sqrt{\alpha^\prime}=0. We
find that the worldsheet theory admits an infinite number of conserved
quantities which are naturally interpreted as spacetime charges and which form
a representation of (two commuting copies of) a Virasoro algebra. Near the
boundary of AdS_3 these charges are found to be isomorphic to the infinite set
of asymptotic Killing vectors of AdS_3 found originally by Brown and Henneaux.
In addition to the spacetime Virasoro algebra, there is a worldsheet Virasoro
algebra that generates diffeomorphisms of the spatial coordinate of the string
worldsheet. We find that if the worldsheet Virasoro algebra has a central
extension then the spacetime Virasoro algebra acquires a central extension via
a mechanism similar to that encountered in the context of the SL(2,R) WZW
model.Our observations are consistent with a recently proposed duality between
bosonic strings on zero radius AdS_d+1 and free field theory in d dimensions.
