  We analyse in detail the X-ray data of the microquasar Cygnus X-3 obtained
during major radio flaring episodes in 2006 with multiple observatories. The
analysis consists of two parts: probing the fast (~ 1 minute) X-ray spectral
evolution with Principal Component Analysis followed by subsequent spectral
fits to the time-averaged spectra (~ 3 ks). Based on the analysis we find that
the overall X-ray variability during major flaring episodes can be attributed
to two principal components whose evolution based on spectral fits is best
reproduced by a hybrid Comptonization component and a bremsstrahlung or
saturated thermal Comptonization component. The variability of the thermal
component is found to be linked to the change in the X-ray/radio spectral
state. In addition, we find that the seed photons for the Comptonization
originate in two seed photon populations that include the additional thermal
emission and emission from the accretion disc. The Comptonization of the
photons from the thermal component dominates, at least during the major radio
flare episode in question, and the Comptonization of disc photons is
intermittent and can be attributed to the phase interval 0.2-0.4. The most
likely location for Comptonization is in the shocks in the jet.
