A strong earthquake shook western Japan on Sunday, injuring at least two people, news reports said. There were no immediate reports of damage. The quake, which struck shortly after 7 p.m. (1000 GMT), had a preliminary magnitude of 6.8 and was centered some 10 kilometers (6 miles) beneath the ocean floor, 110 kilometers (70 miles) off the coast of the Kii peninsula. The quake was felt most strongly in Nara and Wakayama prefectures (states) on the Kii peninsula, which lies about 450 kilometers (280 miles) west of Tokyo. It made tall buildings in central Tokyo sway. Nara and Wakayama police said they had no reports of injuries or damage. An 89-year-old woman and 94-year-old man in Kyoto, just north of the peninsula, were injured, news reports said. A spokesman for the Kyoto prefectural police said they were checking on whether the injuries resulted from the earthquake. A high-speed train service was suspended for about 10 minutes, Kyodo reported. Local commuter lines serving western Japan were also temporarily halted, the news agency said. The Meteorological Agency warned that tsunami _ huge waves triggered by seismic activity _ could hit the coast of Wakayama and told residents to stay inland. Japan, which rests atop several tectonic plates, is among the world's most earthquake-prone countries. A magnitude 6 quake can inflict widespread damage in a populated area.