An advanced neutron detection system for highly localized measurements in nuclear reactor cores was developed and tested in the Laboratory for Reactor Physics and System Behaviour (LRS) at the Ecole polytechnique federale de Lausanne (EPFL), Switzerland, in close collaboration with the Detector group of the Laboratory for Particle Physics (LTP) at the Paul Scherrer Institute (PSI), Switzerland. The miniature-size detector is based on the coupling of a ZnS:(LiF)-Li-6 scintillator/converter screen of 1 mm(2) and 0.2 mm thickness with a 10-m optical fiber, the latter being connected to a silicon photomultiplier (SiPM). In this development version, the output signal is processed via analog read-out electronics. The present work documents the characterization of a detection system prototype in the mixed-radiation fields of the CARROUSEL facility and its testing in the CROCUS zero-power reactor operated at LRS. The fiber-coupled scintillator shows a linear response with the reactor power increase up to 6.5 W (i.e. around 10(8) cm(-2).s(-1) total neutron flux), with a subsequent loss of linearity due to electronic dead time of the analog system. Nevertheless, the detector shows excellent neutron counting capabilities whether compared to other localized detection systems available at LRS, e.g. miniature fission chambers and an sCVD diamond detector.