Kiev, July 21 : A gunman claiming to be armed with explosives on Tuesday seized a passenger bus and was holding 20 people hostage in the western Ukrainian city of Lutsk, police said. The press service of the Security Service of Ukraine Directorate in the Volyn region said the the bus was travelling on the Berestechko-Krasilovka route, reports Xinhua news agency. "The identity of the person who seized the Berestechko-Krasilovka bus this morning is being established. The man does not put any clear demands. "The man does not make contact, and shots from a firearm from time to time. There is information that some kind of explosive device is on the bus," the press service said. The regional police stated that an operational plan "Hostage" is introduced in the region and the city centre, about 250 miles from capital Kiev, is closed to ensure the safety of citizens. The Criminal Investigation Department of Ukraine later said the man has a large number of weapons, including grenades and other automatic weapons. The man hid another bomb in the city, the Department added. Meanwhile, President Volodymyr Zelenskiy confirmed the reports about gunshots and stressed that measures were being taken to resolve the situation without casualties, the Independent newspaper said in a report. In a statement on Facebook, he said: "Gunshots have been heard, the bus is damaged." Anton Heraschenko, the deputy Interior Minister, said the hijacker called the police himself to inform them about the situation. In response to the incident, Interior Minister Arsen Avakov is on his way to Lutsk. /IANS