  We report observations of the flickering variability of the symbiotic
recurrent nova RS~Oph at quiescence in five bands ($UBVRI$). We find evidence
of a correlation between the peak-to-peak flickering amplitude ($\Delta F$) and
the average flux of the hot component ($F_{\rm av}$). The correlation is highly
significant, with a correlation coefficient of 0.85 and a $p$-value of~$\sim
10^{-20}$. Combining the data from all wavebands, we find a dependence of the
type $\Delta F \propto F^k_{\rm av}$, with power-law index $k = 1.02 \pm 0.04$
for the $UBVRI$ flickering of RS~Oph. Thus, the relationship between the
amplitude of variability and the average flux of the hot component is
consistent with linearity. The rms amplitude of flickering is on average 8 per
cent ($\pm2$ per cent) of $F_{\rm av}$. The detected correlation is similar to
that found in accreting black holes/neutron stars and cataclysmic variables.
The possible reasons are briefly discussed. The data are available upon request
from the authors.
