  The magnetic resonance spectrum of spin clusters formed in spin-Peierls
magnets in the vicinity of impurity ions was investigated. The observed
temperature dependences of the effective g-factor and the linewidth of the
electron spin resonance (ESR) in crystals of Cu(1-x)Ni(x)GeO(3) are described
in the model of the exchange narrowing of the two-component spectrum with one
component ascribed to spin clusters and exhibiting an anomalous value of the
$g$-factor and the other related to triplet excitations. An estimation of the
size of the suppressed dimerization region around the impurity ion is obtained
(this region includes about 30 copper ions). The dependence of the effective
g-factor and the ESR linewidth on the impurity concentration at low
temperatures indicates the interaction of clusters.
