  As a part of the ISOPHOT CIRB (Cosmic Infrared Background Radiation) project
we have searched for point-like sources in eight fields mapped at two or three
wavelengths between 90 and 180um. Most sources are previously unknown and based
on the far-infrared (FIR) spectral energy distributions dust-enshrouded,
distant galaxies form a significant fraction of the sources. We present a list
of the new extragalactic FIR-sources and discuss the uncertainties of the
source detection from the ISOPHOT maps. We estimate the source number densities
at 90, 150 and 180um and at flux density levels down to 100mJy to be 10^5, 2
10^5, and 3 10^5 1/sr, respectively. Strong galaxy evolution models are in best
agreement with our results, although the number of detections exceeds most
model predictions. No-evolution models can be rejected at a high confidence
level. Comparison with COBE results indicates that at 90um the detected sources
correspond to some 20% of the extragalactic background light. At longer
wavelengths the corresponding fraction is closer to 10%.
