HIGHER SPINS DYNAMICS IN CLOSED STRING THEORY

A general sigma-model-type string action including both massless and m assive higher spins background fields is suggested. Field equations fo r background fields follow from the requirement of quantum Weyl invari ance. It is shown that renormalization of the theory can be produced l evel by level. A detailed consideration of background fields structure and corresponding fields equations is given for the first massive lev el of the closed bosonic string.