Kiev - An armed man carrying explosives has taken around 20 passengers hostage on a bus in the western Ukrainian city of Lutsk, police said Tuesday. The head of the local police service said shots were heard at the scene but no injuries have been reported so far. Law enforcement has cordoned off the centre of Lutsk, a city in western Ukraine some 400 kilometres (250 miles) from the capital Kiev, and advised residents not to leave their homes or places of work. Police said the SBU security services had surrounded the minibus after two shots were fired from it towards law enforcement.