Undersea Japan earthquake
Powerful 8.5 undersea earthquake hits eastern Japan's coastUSGS

A strong offshore earthquake has shaken eastern Japan with tremors felt in Tokyo.

The US Geological Survey said the 7.8-magnitude earthquake was centred 874km (543 miles) from Tokyo, and struck at about 18:30 local time (11:30 GMT).

Buildings in the capital swayed for almost a minute as the quake built in intensity, with car alarms set off, AFP news agency reported.

No tsunami warning has been issued and so far no casualties were reported.

According to early reports, the earthquake was observed in Chichi-shima, Bonin Islands, Japan at 11:23:00.00 UTC.

The epicentre was 676 kilometres (422 miles) below the Earth's surface, the US Geological Survey said.

Yoshiyuki Sasamoto, who runs a traditional guest house on Chichijima, one of the closest inhabited places to the epicenter, told AFP the shaking had been violent.

"Initially a weaker quake hit and it stopped. Then the big one came. It was so strong that I couldn't stand still and couldn't walk," he said.

The two runways at Narita Airport, the main international gateway to Tokyo, were closed temporarily to carry out inspections. Trains in Tokyo were also delayed and a football match in the city was suspended briefly.

More about earthquakes