Tokyo:
A powerful 7.1-magnitude earthquake late on Thursday hit the same area of Japan that was ravaged by disaster a month ago, seismologists said, prompting a local tsunami alert.
Power was cut to parts of the northeast of the country, much of which is still struggling with the effects of the monster tsunami that roared ashore four weeks ago.
The new quake caused a handful of injuries, national broadcaster NHK said, but there were no reported deaths. The tsunami alert was later cancelled after no deadly wave materialised.
Workers battling to control the stricken Fukushima Daiichi nuclear plant on the northeast coast were temporarily ordered to evacuate, plant operator Tokyo Electric Power Co. (TEPCO) said.
The evacuation order came less than 24 hours after they began pumping nitrogen, an inert gas, into reactor No. 1, where engineers were concerned a build-up of hydrogen might react with oxygen to cause an explosion.
Work at the plant was remotely controlled and was continuing, the company said.
A TEPCO spokesman told a press conference there was "no information immediately indicating any abnormality at Fukushima Daiichi plant."
A nuclear safety agency official told reporters: "There are no abnormal readings at the Fukushima Daiichi's monitoring posts", adding: "We have not seen any problem... with regard to the injection of nitrogen."
The official said some external power sources used to cool reactor cores had been lost at plants in Onagawa in Miyagi prefecture and at Rokkasho and Higashidori in Aomori prefecture, but at least one emergency source remained operational at each.
The loss of external power sources at Fukushima Daiichi in the March 11 tsunami left reactor cores heating up uncontrollably, resulting in the world's worst nuclear emergency since Chernobyl.
There was no indication that Thursday's loss of power was causing a problem at any of the nuclear plants.
The tremor hit at 11:32 pm local time (1432 GMT) with an offshore epicentre 66 kilometres (40 miles) east of Sendai, a city severely impacted by the March 11 quake and tsunami, according to the US Geological Survey.
Japan's Meteorological Agency promptly issued a tsunami alert for the Pacific coast, saying waves of up to two metres (six feet) could hit the shoreline, but the alert was cancelled 83 minutes after the quake.
Footage from broadcaster NHK showed power was off in parts of Sendai, a regional commercial hub badly shaken last month's double disaster.
An AFP photographer in Kitakami city in Iwate prefecture reported that power had gone off following Thursday's quake.
Jiji Press news agency said shortly after midnight there were five fires and 13 gas leaks in Sendai city, according to the Miyagi prefectural office.
In Iwate prefecture, local authorities ordered some 500 households to evacuate, NHK said. The broadcaster also reported three fires in Iwate and Miyagi prefectures.
The quake had a depth of 49 kilometres, the USGS said. Although the epicentre was 330 kilometres from Tokyo, it shook buildings in the Japanese capital.
A Meteorological Agency official said the tremor was an aftershock of the Match 11 tremor, and data on the organisation's website showed that it was one of the most powerful.
Around 400 strong aftershocks have rocked Japan since the 9.0 magnitude quake last month and the tsunami it spawned, which killed 12,500 people and left around 15,000 unaccounted for.
Before the tremor chief government spokesman Yukio Edano indicated Tokyo was considering widening the 20-kilometre (12-mile) evacuation zone around the stricken plant, a week after a UN nuclear watchdog said it should be increased.
"The existing safety standards for local residents are that an evacuation order is issued if there is a possibility that they might receive radiation 50 millisieverts or above," he said.
"The standard assumed that a high level of radiation is emitted temporarily. We are discussing how best to issue evacuation orders based on data and standards for accumulative radiation," Edano said.
Around 3,400 people are unaccounted for along the 40-kilometre stretch of coast covered by the exclusion zone and on Thursday, around 300 police began searching for bodies in the the outer 10-kilometre band of the zone.
Television pictures showed officers in full body suits entering the area, while a police spokesman said all officers were armed with radiation meters.
The Bank of Japan on Thursday warned of pressures as a result of the triple disaster and bolstered funding for quake-hit areas, unveiling a 1.0 trillion yen ($11.7 billion) scheme to keep banks in affected areas liquid.
The Bank of Japan also downgraded its view of the economy due to last month's disasters.
Power was cut to parts of the northeast of the country, much of which is still struggling with the effects of the monster tsunami that roared ashore four weeks ago.
The new quake caused a handful of injuries, national broadcaster NHK said, but there were no reported deaths. The tsunami alert was later cancelled after no deadly wave materialised.
Workers battling to control the stricken Fukushima Daiichi nuclear plant on the northeast coast were temporarily ordered to evacuate, plant operator Tokyo Electric Power Co. (TEPCO) said.
The evacuation order came less than 24 hours after they began pumping nitrogen, an inert gas, into reactor No. 1, where engineers were concerned a build-up of hydrogen might react with oxygen to cause an explosion.
Work at the plant was remotely controlled and was continuing, the company said.
A TEPCO spokesman told a press conference there was "no information immediately indicating any abnormality at Fukushima Daiichi plant."
A nuclear safety agency official told reporters: "There are no abnormal readings at the Fukushima Daiichi's monitoring posts", adding: "We have not seen any problem... with regard to the injection of nitrogen."
The official said some external power sources used to cool reactor cores had been lost at plants in Onagawa in Miyagi prefecture and at Rokkasho and Higashidori in Aomori prefecture, but at least one emergency source remained operational at each.
The loss of external power sources at Fukushima Daiichi in the March 11 tsunami left reactor cores heating up uncontrollably, resulting in the world's worst nuclear emergency since Chernobyl.
There was no indication that Thursday's loss of power was causing a problem at any of the nuclear plants.
The tremor hit at 11:32 pm local time (1432 GMT) with an offshore epicentre 66 kilometres (40 miles) east of Sendai, a city severely impacted by the March 11 quake and tsunami, according to the US Geological Survey.
Japan's Meteorological Agency promptly issued a tsunami alert for the Pacific coast, saying waves of up to two metres (six feet) could hit the shoreline, but the alert was cancelled 83 minutes after the quake.
Footage from broadcaster NHK showed power was off in parts of Sendai, a regional commercial hub badly shaken last month's double disaster.
An AFP photographer in Kitakami city in Iwate prefecture reported that power had gone off following Thursday's quake.
Jiji Press news agency said shortly after midnight there were five fires and 13 gas leaks in Sendai city, according to the Miyagi prefectural office.
In Iwate prefecture, local authorities ordered some 500 households to evacuate, NHK said. The broadcaster also reported three fires in Iwate and Miyagi prefectures.
The quake had a depth of 49 kilometres, the USGS said. Although the epicentre was 330 kilometres from Tokyo, it shook buildings in the Japanese capital.
A Meteorological Agency official said the tremor was an aftershock of the Match 11 tremor, and data on the organisation's website showed that it was one of the most powerful.
Around 400 strong aftershocks have rocked Japan since the 9.0 magnitude quake last month and the tsunami it spawned, which killed 12,500 people and left around 15,000 unaccounted for.
Before the tremor chief government spokesman Yukio Edano indicated Tokyo was considering widening the 20-kilometre (12-mile) evacuation zone around the stricken plant, a week after a UN nuclear watchdog said it should be increased.
"The existing safety standards for local residents are that an evacuation order is issued if there is a possibility that they might receive radiation 50 millisieverts or above," he said.
"The standard assumed that a high level of radiation is emitted temporarily. We are discussing how best to issue evacuation orders based on data and standards for accumulative radiation," Edano said.
Around 3,400 people are unaccounted for along the 40-kilometre stretch of coast covered by the exclusion zone and on Thursday, around 300 police began searching for bodies in the the outer 10-kilometre band of the zone.
Television pictures showed officers in full body suits entering the area, while a police spokesman said all officers were armed with radiation meters.
The Bank of Japan on Thursday warned of pressures as a result of the triple disaster and bolstered funding for quake-hit areas, unveiling a 1.0 trillion yen ($11.7 billion) scheme to keep banks in affected areas liquid.
The Bank of Japan also downgraded its view of the economy due to last month's disasters.
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