An armed man hijacked a bus and took 20 passengers hostage in eastern Ukraine Tuesday.

Police received an emergency call saying that a gunman with explosives had barricaded himself inside the bus in the town of Lutsk. Negotiations are underway between the hijacker and the police by phone. The hijacker has claimed that the bus is rigged to explode.

The Ukrainskaya Pravda newspaper reported that police have found online posts by the gunman expressing his“dissatisfaction with the system in Ukraine.”

Ukrainian President Volodymyr Zelenskiy called the incident "alarming" and stated that police are doing everything in their power to resolve the situation without casualties.