Ukraine’s president on Thursday said Russian hackers have conducted 6,500 cyberattacks on Ukrainian institutions over the past two months. “The investigation of a number of incidents indicated the complicity directly or indirectly of Russian security services waging a cyberwar against our country,” Ukrainian President Petro Poroshenko told security and defense officials. “Acts of terrorism and sabotage on critical infrastructure facilities remain possible today,” he warned. Ukraine’s government institutions have frequently been targeted by hackers throughout the conflict in the country's east. This month, the defense and finance ministries were hit, as well as the state treasury. Late last year, electricity was knocked out for thousands of residents in western Ukraine in an attack on a power grid, which authorities believe Russia was responsible for. Poroshenko’s warning came on the same day the U.S. imposed sanctions on Russian officials and expelled dozens of diplomats over cyberattacks and hacking during the U.S. presidential election.