Sept. 26 (Bloomberg) -- An earthquake of magnitude 8 shook Japan's northern main island of Hokkaido just before dawn, injuring 236 people and causing power outages, flight cancellations and a fire at an oil refinery.

The Japan meteorological office issued a tsunami warning for the Pacific coastal areas of Hokkaido and northern Honshu. Waves of about 1.3 meters (4 feet) struck the coast after the tremor. Repeated tsunamis are possible, the agency said. U.S. officials warned tsunamis could strike as far away as Russia or Guam.

The quake, the largest recorded in the world this year, was centered about 65 miles (105 kilometers) off the coast of Hokkaido, according to measurements by the U.S. National Earthquake Information Center in Golden, Colorado. The town nearest to the quake's epicenter is Kushiro, on Hokkaido.

Japan Airlines System Corp. and All Nippon Airways Co., the country's two biggest carriers, canceled flights to and from Kushiro airport, after air traffic control was affected by the earthquake.

Japan Airlines's Japan Air System Co. unit canceled six flights, including four between Kushiro and Tokyo's Haneda airport and two between Kushiro and the central city of Nagoya, spokesman Hirohide Ishikawa said. All Nippon Airways canceled two flights between Haneda and Kushiro airport, said spokesman Kunio Shibata.

``Shinkansen'' high-speed trains operated by East Japan Railway Co. in northern Japan are running normally, said spokesman Hideki Fukaya.

Second Quake

``The horizontal oscillation was very strong,'' Kushiro General Affairs Division Assistant Director Yasuharu Nakai said. About 9,100 homes in the Hoshigaura area are without power and there have been reports of injuries, Nakai said.

A second quake, with a preliminary magnitude of 6, was recorded in southern Hokkaido just over an hour later, Kyodo News reported. Aftershocks of magnitude 3.3 and 3.7 were detected in Alaska, the U.S. earthquake center said.

About 166 people had been injured in the Kushiro, Obihiro and other areas in Hokkaido, according to NHK news. Hokkaido experienced earthquakes of similar magnitudes in 1993 and 1994.

Idemitsu Kosan Co., Japan's second biggest oil refiner, said it shut a 140,000-barrel-a-day refinery in Hokkaido after a fire caused by the earthquake.

The quake also triggered an automatic shutdown of Hokkaido Electric Co.'s Tomato-Atsuma power station, according to Kyodo. About 16,300 households were without electricity as of 8 a.m., Kyodo said. Japan's military is preparing to provide water in an area where supplies were cut off, NHK said.

Hotel Shaken

At the Northland Hotel in Obihiro, less than 50 miles from the coast, rooms were littered with broken glass, toppled light stands and televisions knocked to the floor, according to Takego Miakawa, a receptionist at the hotel. All of the guests are safe, and there is no structural damage, he said.

The quake took place at about 4:50 a.m. Japan time, Waverly Person, a geophysicist at the U.S. quake center said. The epicenter was located about 490 miles (788 kilometers) north-northeast of Tokyo, he said.

Last Updated: September 25, 2003 22:01 EDT