A magnitude-6.6 earthquake struck a large area of western Japan on Friday, but no tsunami warnings were issued, authorities said.There were no immediate reports of casualties or damage to property.The quake prompted train services in the west of the country to be suspended, broadcaster NHK reported.The epicentre of the 2:07 pm (0507 GMT) quake was located in the middle of Tottori prefecture, at a depth of 10 kilometres, Japan's Meteorological Agency said.