Powerful earthquake hits northeastern Japan

Tens of thousands of Japanese households have remained without power morning after a magnitude 7.4 quake struck shortly before midnight, throwing a swathe of northeastern Japan into darkness, severing key transportation links and killing four.

Prime Minister Fumio Kishida said on Thursday four people had died and that the government would be on high alert for the possibility of further strong tremors over the next two to three days.

Companies including Toyota Motor Corp and chipmaker Renesas Electronics Corp raced to assess the impact, with any supply chain disruption likely to add pressure to strain ed global output of smartphones, electronics and automobiles.

About 300 km (186 miles) south of Fukushima, areas of the capital Tokyo lost power immediately after the quake, though most regained it within three hours.

But some 5,775 households serviced by Tohoku Electric Power Co Inc in the northeast remained without electricity as of noon local time (0300 GMT) on Thursday, though the firm said it expected most will have supply restored later in the day.

At least 107 people were reported injured, several seriously, with 4,300 households also still without water by mid-morning.

Residents of one Fukushima city formed a long queue to fill up plastic tanks with water for use at home. Renesas, a major supplier of automotive chips, said it had suspended production at two semiconductor plants and partially stopped output at a third.

Anniversary of massive quake

A tsunami warning for waves of up to a metre in parts of northeast Japan was lifted in the early hours of Thursday after authorities recorded water levels up to 30 cm higher than usual in some areas.

Multiple smaller jolts continued to hit the region throughout the night and morning on Thursday.

Reports of damage appeared relatively minor, in a country with tough building codes intended to protect against devastation from frequent earthquakes, and officials said there were no abnormalities at nuclear plants.

The quake struck at a depth of 60 kilometres off the Fukushima coast and was preceded minutes earlier by another strong 6.1-magnitude shake in the same area, Japan's Meteorological Agency said.

The night-time shaking came just days after Japan marked the 11th anniversary of a massive quake that triggered a deadly tsunami and the Fukushima nuclear catastrophe.