  The identification of major contributors to the locally observed fluxes of
Cosmic Rays (CRs) is a prime objective towards the resolution of the
long-standing enigma of CRs. We report on a compelling similarity of the energy
and radial distributions of multi-TeV CRs extracted from observations of very
high energy (VHE) $\gamma$-rays towards the Galactic Center (GC) and two
prominent clusters of young massive stars, Cyg~OB2 and Westerlund~1. This
resemblance we interpret as a hint that CRs responsible for the diffuse VHE
$\gamma$-ray emission from the GC are accelerated by the ultracompact stellar
clusters located in the heart of GC. The derived $1/r$ decrement of the CR
density with the distance from a star cluster is a distinct signature of
continuous, over a few million years, CR injection into the interstellar
medium. The lack of brightening of the $\gamma$-ray images toward the stellar
clusters excludes the leptonic origin of $\gamma$-radiation. The hard, $\propto
E^{-2.3}$ type power-law energy spectra of parent protons continues up to
$\sim$ 1 PeV. The efficiency of conversion of kinetic energy of stellar winds
to CRs can be as high as 10 percent implying that the young massive stars may
operate as proton PeVatrons with a dominant contribution to the flux of highest
energy galactic CRs.
