  We study the radio continuum emission of four galaxies experiencing
ram-pressure stripping in four clusters of the Shapley supercluster at redshift
z~0.05. Multi-band (235-1367 MHz) radio data, complemented by integral-field
spectroscopy, allow us to detect and analyse in detail the non-thermal
component both in the galaxy discs and the radio continuum tails. Three
galaxies present radio continuum tails which are tens of kiloparsecs long. By
deriving the radio spectral index in the inner and outer tails and comparing
our findings with the distribution of the extraplanar ionised gas and the
results of N-body/hydrodynamical simulations, we demonstrate that these tails
are caused by the ram pressure which, together with the ionised gas, sweeps the
magnetic field from the galaxy discs. We suggest that the radio continuum
emission in these tails can be differently powered by (i) in situ star
formation; (ii) relativistic electrons stripped from the disc; (iii) shock
excitation or a combination of them. All the ram-pressure stripped galaxies are
found in environments where cluster-cluster interactions occurred and/or are
ongoing thus strongly supporting the thesis that cluster and group collisions
and mergers may locally increase the ram pressure and trigger hydrodynamical
interactions between the intracluster medium and the interstellar medium of
galaxies.
