  We present Swift observations of 31 sources from the SMS4 catalog, a sample
of 137 bright radio sources in the Southern Hemisphere. All these sources had
no Chandra or XMM-Newton observations: 24 of these were observed with Swift
through a dedicated proposal in 2015, and data for the remaining seven were
retrieved from the Swift archive. The reduction and analysis of data collected
by the Swift X-ray Telescope (XRT) led to 20 detections in the 0.3--10 keV
band. We provide details of the X-ray emission in this band for these 20
detections, as well as upper limits for the remaining 11 SMS4 sources. When
statistics allowed, we investigated the extent of the X-ray emission, the
hardness ratio, and we carried out a spectral analysis. We matched the 20 X-ray
detected sources with infrared (AllWISE, CatWISE2020) and optical (GSC 2.3.2,
DES DR2) catalogs to establish associations with infrared and optical sources,
and compared our results with previously published counterparts in these bands.
Requiring a detection in both the infrared and the optical bands to establish a
candidate counterpart for our X-ray detections, we obtain reliable counterparts
for 18 sources, while the remaining two sources need further investigation to
establish firm identifications. We find that ~35% of all the SMS4 sources lie
below the lower limit of 10.9 Jy for the flux density at 178 MHz. We present
the list of 56 SMS4 sources that in 2022 March remain to be observed in the
X-rays with narrow-field instruments.
