  Monopole-antimonopole pairs connected by strings and monopole-string networks
with $N>2$ strings attached to each monopole can be formed at phase transitions
in the early universe. In such hybrid defects, monopoles accelerate under the
string tension and can reach ultrarelativistic Lorentz factors, $\gamma\gg 1$.
We study the radiation of gauge quanta by accelerating monopoles. For monopoles
with a chromomagnetic charge, we also discuss the high-energy hadron production
through emission of virtual gluons and their subsequent fragmentation into
hadrons. The relevant parameter for gauge boson radiation is $M/a$, where $M$
is the boson mass and $a$ is the proper acceleration of the monopole. For $M\ll
a$, the gauge bosons can be considered as massless and the typical energy of
the emitted quanta is $E\sim\gamma a$. In the opposite limit, $M\gg a$, the
radiation power is exponentially suppressed and gauge quanta are emitted with a
typical energy $E\sim\gamma M$ in a narrow range $\Delta E/E\sim (a/M)^{1/2}$.
Cosmological monopole-string networks can produce photons and hadrons of
extremely high energies. For a wide range of parameters these energies can be
much greater than the Planck scale.
