  The extended high-energy gamma-ray (>100 MeV) emission occurring after the
prompt gamma-ray bursts (GRBs) is usually characterized by a single power-law
spectrum, which has been explained as the afterglow synchrotron radiation. We
report on the Fermi Large Area Telescope (LAT) observations of the >100 MeV
emission from the very bright and nearby GRB 130427A, up to ~100 GeV. By
performing time-resolved spectral fits of GRB 130427A, we found a strong
evidence of an extra hard spectral component above a few GeV that exists in the
extended high-energy emission of this GRB. This extra spectral component may
represent the first clear evidence of the long sought-after afterglow inverse
Compton emission. Prospects for observations at the very high-energy
gamma-rays, i.e., above 100 GeV, are described.
