Disaster-weary Japan was rattled yesterday by another strong seabed quake with a magnitude of 6.3.

The earthquake triggered a temporary tsunami warning and sent people diving for cover.

The quake struck in the Pacific Ocean not far from the epicentre of the March 11 quake-tsunami disaster that killed more than 20,000 people and triggered the world’s worst nuclear crisis since Chernobyl 25 years ago.

Sirens again wailed along the devastated northeast coast, where people have been terrified by hundreds of aftershocks over the past five months. The quake also caused buildings to sway across Tokyo.

The tremor struck 283 kilometres northeast of Tokyo and 99 km southeast of tsunami-hit Sendai city at a depth of about 43 km at 2.36 pm (0536 GMT), according to the US Geological Survey.

Japan’s meteorological agency measured the quake at a magnitude of 6.8.

The agency also issued a 50-centimetre tsunami warning but called it off after only very small waves were seen along the coast.

The operator of the crippled Fukushima nuclear plant, Tokyo Electric Power Company (Tepco), quickly said there were no reports of fresh damage or abnormalities after the latest quake.

Tepco spokeswoman Ai Tanaka said that emergency workers were briefly evacuated but that “there is no abnormality in our cooling operations at the plant. Radiation gauges did not show any abnormal change either.”

The Pacific Tsunami Warning Centre said there was no threat of a destructive widespread tsunami in the broader Pacific Ocean.

In the coastal city of Ishinomaki, where more than 4,000 people were killed in the March 11 disaster, tsunami sirens wailed, buildings shook violently and some office workers dived for cover under their desks.

There were no reports of injuries or damage following the quake.