TOKYO - A strong earthquake with a magnitude of 6.9 struck off northeastern Japan on Tuesday, the US Geological Survey said, and small waves were reported along the northern coast after Japan issued a tsunami warning.
Japanese broadcaster NHK said small waves of between 10 cm and 20 cm (4-8 inches) reached the coast off Iwate prefecture, some 600 km (370 miles) from Tokyo. NHK said thousands of residents in the area were ordered to evacuate.
There were no immediate reports of damage or injuries. "We are using the emergency broadcast to advise people to keep away from the sea ... the quake was pretty strong and lasted a long time so I thought there would be a tsunami warning," Kozo Hirano, an Otsuchi Town official in Iwate, told NHK.
Live video from ports on the Iwate coast showed small waves lapping on the shore. Towns along the northeastern coast of Japan had been levelled in a devastating tsunami in March 2011.
Tuesday's quake was measured at a depth of about 10 km (6 miles). The Pacific Tsunami Warning Center in Hawaii said there was no danger of a Pacific-wide tsunami but the Japan Meteorological Agency issued a tsunami advisory for Iwate prefecture after the quake.
Tohoku Electric Power Co, which operates the Onagawa and Higashidori nuclear plants in nearby Miyagi and Aomori prefectures, said it saw no irregularities at the facilities after the quake.
All 48 of Japan's nuclear reactors remain offline after a March 2011 earthquake and tsunami, which triggered the Fukushima nuclear disaster in northeastern Japan.
A spokesman for Tokyo Electric Power Co, the operator of Fukushima Daiichi and Fukushima Daini nuclear plants, said there were no irregularities at the plants. The quake was felt only weakly in the area, he said.
Unlisted Japan Nuclear Fuel Ltd also said there were no irregularities recorded at its nuclear fuel reprocessing facility or other plants in Aomori.
Earthquakes are common in Japan, one of the world's most seismically active areas. Japan accounts for about 20 per cent of the world's earthquakes of magnitude 6 or greater.