A strong earthquake centred off the coast of northeastern Japan shook buildings as far away as Tokyo on Friday and led to a tsunami warning for coastal areas.
The earthquake hit in the same area as a devastating quake and tsunami in March last year that killed nearly 20,000 people and triggered the world's worst nuclear crisis in 25 years.
The quake had a preliminary magnitude of 7.3, the U.S. Geological Survey said, adding that there was no risk of a widespread tsunami. There were no immediate reports of death or injury.
The quake measured a "lower 5" on Japan's scale of one to seven in Miyagi prefecture, meaning there might be some damage to roads and houses that are less quake resistant.
The scale measures the amount of shaking and in that sense gives a better idea of possible damage than the magnitude. The quake registered a 4 in Tokyo.
A warning of a one-metre tsunami was issued for the coast of Miyagi, at the centre of the devastation from the March 2011 disaster.
That quake, which measured 9.0, triggered fuel-rod meltdowns at the Fukushima nuclear plant, causing radiation leakage, contamination of food and water and mass evacuations. Much of the area is still free of people.
The government declared in December that the disaster was under control.
Tokyo Electric Power Co, the operator of the Fukushima nuclear plant, reported no irregularities at its nuclear plants after the latest quake.
Prime Minister Yoshihiko Noda cancelled campaigning in Tokyo ahead of a Dec. 16 election and was on his way back to his office, but there was no immediate plan to hold a special cabinet meeting.
Public spending on quake-proofing buildings is a big election issue.
Japanese were posting photos of their TV screens with tsunami warnings on Facebook, asking each other whether they're safe, confirming their whereabouts.
"It shook for a long time here in Tokyo, are you guys all all right?" posted Eriko Hamada, enquiring about the safety of her friends.
Phone lines were overloaded and it was difficult to contact residents of Miyagi.
"Owing to the recent earthquake, phone lines are very busy, please try again later," the phone operator said.
The yen rose against the dollar and the euro on the news, triggering some safe-haven inflows into the Japanese currency.