We use observations of the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) to search for gamma-ray and hard X-ray emission associated with the gravitational wave events discovered during the first and the second scientific runs of Advanced LIGO and Advanced Virgo. The highly eccentric orbit of INTEGRAL ensures high duty cycle, long-term stable background, and unobstructed view of nearly the entire sky. This enables us to use a combination of INTEGRAL instruments (SPI-ACS, IBIS/Veto, and IBIS) to search for a hard X-ray electromagnetic signal in the full high-probability sky region for almost every single LIGO trigger.

The fraction of the energy promptly released in gamma-rays in 75 keV - 2 MeV energy range in the direction of the observer is constrained to be less than one millionth of the gravitational wave energy, in the majority of the localization region. Moreover, in the case of LVT151012 INTEGRAL high-energy imaging instruments, IBIS, SPI, and JEM-X, provided the unique opportunity to search also for long-lasting electromagnetic counterparts of this event over 3 decades in energy, from 5 keV to 8 MeV.