  We discuss ultra-high energy (UHE) cosmic rays (CR) from minor sources and
their possible contribution to the extragalactic diffuse gamma-ray emission. As
an illustration of minor sources we consider possible specific type of active
galactic nuclei (AGN) in which supermassive black hole is surrounded by a super
strong magnetic field of 10^(10)-10^(11) Gs. In this model we have calculated
CR energy spectra at the Earth and intensity of cascade quanta produced by CRs
in extragalactic space. Proceeding from numerical results and the data by
Pierre Auger Observatory and Telescope Array it is shown that these AGNs make a
negligible contribution to the UHECR flux at the Earth. However CRs from the
AGNs produce significant gamma-ray flux as compared to extragalactic diffuse
gamma-ray emission measured by Fermi LAT. We conclude that UHECRs from minor
sources can contribute noticeably to extragalactic gamma-ray emission.
