Detection of the atmospheric neutrino flux with the first detection units of KM3NeT/ORCA

The KM3NeT Collaboration is currently constructing two next-generation neutrino detectors in the Mediterranean Sea, aiming at: investigating the fundamental properties of neutrinos by measuring atmospheric neutrino oscillations at GeV energies (ORCA); detecting high-energy cosmic neutrinos from Galactic and extra-Galactic sources (ARCA). The first six detection units of the KM3NeT/ORCA detector have been deployed off-shore the French coast. The selection of a high-purity neutrino sample obtained already with a limited number of active detection units and the first preliminary physics results obtained with this sample of atmospheric neutrino events will be presented in this contribution.