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Abridged. Methods. We made use of the Karl G. Jansky Very Large Array (VLA)in the B configuration at K band, and in the A configuration at both Ku and Cbands, in order to image the radio continuum emission towards 25 H$_2$O masersites with an angular resolution and thermal rms of the order of $0.1''$ and 10$\mu$Jy beam$^{-1}$, respectively. These targets add to our pilot study of 11maser sites presented in Moscadelli et al. (2016). The sample of H$_2$O masersites was selected among those regions having an accurate distance measurement,obtained through maser trigonometric parallaxes, and H$_2$O maser luminositiesin excess of 10$^{-6}$ L$_{\odot}$. Results. We present high-resolution radiocontinuum images of 33 sources belonging to 25 star-forming regions. In eachregion, we detect radio continuum emission within a few 1000 au of the H$_2$Omasers' position; 50% of the radio continuum sources are associated withbolometric luminosities exceeding 5 $\times$ 10$^{3}$ L$_{\odot}$, includingW33A and G240.32$+$0.07. We provide a detailed spectral index analysis for eachradio continuum source, based on the integrated fluxes at each frequency, andproduce spectral index maps with the multi-frequency-synthesis deconvolutionalgorithm of CASA. The radio continuum emission traces thermal bremsstrahlungin (proto)stellar winds and jets, with flux densities at 22 GHz below 3 mJy,and spectral index values between $-0.1$ and 1.3. We prove a strong correlation($r>$0.8) between the radio continuum luminosity (L$_{\rm rad}$) and the H$_2$Omaser luminosity (L$_{\rm H_2O}$) of ($\rm L_{8GHz}/mJy\timeskpc^2)=10^{3.8}\times(L_{H_2O}/L_{\odot})^{0.74}$. Since H$_2$O masers areexcited through shocks driven by (proto)stellar winds and jets, these resultsprovide support to the idea that the radio continuum emission around youngstars is dominated by shock-ionization.

Protostellar Outflows at the EarliesT Stages (POETS). I. Radio thermal jets at high resolution nearby H$_2$O maser sources