Several strong earthquakes shook northwestern Japan in less than an hour on Saturday, toppling homes, causing blackouts, cutting water services and derailing a bullet train. At least nine people were reported injured. The quakes - the first of which measured a magnitude 6.8 and struck at 5:56 p.m. - were centered near Ojiya city about 12 miles beneath the earth's surface, the Meteorological Agency said. Ojiya is in the state of Niigata, about 160 miles northwest of Tokyo. The other tremors, which hit intermittently over roughly 40 minutes, included a magnitude 6.2 and 5.9 quake, and less severe aftershocks followed, the agency said. Media reports said the shaking in some parts of Niigata was so severe that people had difficulty standing. Buildings hundreds of miles away in Tokyo swayed several times for up to a minute at one point. Five people were reported injured by objects that had fallen from shelves in Ojiya, public broadcaster NHK said. Four others were hurt in nearby Tokamachi city, and homes in other towns and cities had collapsed, NHK said. Sewage and water mains burst, power and telephone services were down and roads cracked, officials told Japanese media. Near Ojiya, trees and soil on a hillside sheared away, burying several cars on a road below, NHK said. The jolt triggered an automatic safety device that halted most train services, according to media reports. Railway officials said a bullet train had derailed near Nagaoka city, in Niigata prefecture, and another express train headed to Niigata had jumped its tracks and was lying on its side. It wasn't clear how many passengers were aboard the trains or whether there were any injuries. The Meteorological Agency said there was no threat of tsunami, potentially dangerous waves triggered by seismic activity. The temblor came just days after Japan's deadliest typhoon in more than a decade, which left 77 dead and more than a dozen others missing. Japan, which rests atop several tectonic plates, is among the world's most earthquake-prone countries. A magnitude-6 quake can cause widespread damage to homes and other buildings if centered in a heavily populated area.