FROM - RANASINGHE 2 ''Tokyo (CNN) — The most powerful earthquake to hit Japan in at least 100 years struck offshore the island nation on Friday, collapsing buildings, touching off widespread fires and unleashing walls of water up to 30 feet high. The waves swept across rice fields, engulfed towns, dragged houses onto highways, tossed cars and boats like toys -- reaching as far about six miles (10 kilometers) inland in Miyagi Prefecture on Japan’s east coast. Hundreds of people were dead and hundreds more missing, Japanese media reported, citing local and national police. Tens of thousands of people were displaced, according to Japan's Kyodo News agency. Prime Minister Naoto Kan said the enormously powerful earthquake had caused tremendous damage over a wide area. The 8.9-magnitude quake prompted the US National Weather Service to issue tsunami warnings for at least 50 countries and territories, although initial reports as the waves reached locations outside of Japan indicated no damage. The epicenter was offshore, about 230 miles (370 kilometers) from Tokyo, the United States Geological Survey said. Residents there continued to feel aftershocks hours after the quake. More than 30 aftershocks followed, with the strongest measuring 7.1. It appeared that concerns about a cooling failure at the Fukushima nucleGallery: Witness deals with quake terror Buildings, windows damaged in Japan Japanese broadcasters reported collapsed buildings, power outages and transportation