Disaster-weary Japan was rattled by another strong quake on Friday, which measured at a preliminary magnitude of 6.8, triggered a tsunami warning and sent people diving for cover.
The quake struck the Pacific seabed 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, and the quake also caused buildings to sway across Tokyo.
The tremor struck at a depth of 20 kilometres (12 miles) off the Pacific coast, 80 kilometres southeast of Miyagi prefecture, at 2:36pm (0536 GMT), according to a preliminary report from the meteorological agency.
The agency issued a 50-centimetre tsunami warning but called it off after only very small waves were seen lapping at 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 Center 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 strongly and some office workers dived for cover under their desks.
An hour after the quake there were no reports of injuries or damage.
"We are in the middle of gathering information about any damage," Yumi Sato, a spokeswoman for the Ishinomaki City Office, said by telephone.
"We called on citizens through the disaster public address system to evacuate to high ground.
"Inside the city office, no objects fell down due to the quake. But it shook very much and a number of employees hid below their desks because we all remembered the March earthquake."
Japan, located at the junction of four tectonic plates, experiences 20 percent of the strongest quakes recorded on Earth each year.