Optical and near-infrared observations of the gamma-ray burst GRB 031203 , at z = 0.1055 , are reported .
A very faint afterglow is detected superimposed to the host galaxy in our first infrared JHK 
observations , carried out \sim 9 hours after the burst .
Subsequently , a rebrightening is detected in all bands , peaking in the R band about 18 rest-frame days after the burst .
The rebrightening closely resembles the light curve of a supernova like SN 1998bw , assuming that the GRB and the SN went off almost simultaneously , but with a somewhat slower evolution .
Spectra taken close to the maximum of the rebrightening show extremely broad features as in SN 1998bw .
The determination of the absolute magnitude of this SN ( SN 2003lw ) is difficult owing to the large and uncertain extinction , but likely this event was brighter than SN 1998bw by 0.5 mag in the VRI bands , reaching an absolute magnitude M _ { V } = -19.75 \pm 0.15 .