6.1-magnitude quake shakes Tokyo region
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The quake sent buildings swaying and an emergency warning blaring from the phones of local residents, intended to give them time to take shelter.
Initial information from the JMA put the epicentre of the quake in Chiba prefecture, east of Tokyo, and said it struck at 10:41pm (1341 GMT) with a depth of 80 kilometres. There were no immediate reports of injuries or damage.
The US Geological Survey put the quake's strength at magnitude 5.9 with a depth of 61 kilometres.
Some bullet and local train services were halted as a precaution after the quake, but local media reporting from locations in and around Tokyo said there did not appear to be any serious impact from the tremblor.
Checks were also underway at regional nuclear plants, but there were no reports of abnormalities.
Several hundred Tokyo homes were also reportedly without power after the earthquake struck.
The quake was comparatively strong compared to recent quakes in Tokyo, which like much of Japan regularly experiences seismic activity.
Newly elected Prime Minister Fumio Kishida in a tweet urged residents to "please take action to save lives while checking the latest information."
Japan sits on the Pacific "Ring of Fire", an arc of intense seismic activity that stretches through Southeast Asia and across the Pacific basin.
Last week, a 6.1-magnitude quake struck off Japan's northwestern coast, also causing no damage.
The country is regularly hit by quakes, and has strict construction regulations intended to ensure buildings can withstand strong tremors.
But it remains haunted by the memory of the March 11, 2011 undersea quake that triggered a deadly tsunami and unleashed the Fukushima nuclear accident.
The tsunami left some 18,500 dead or missing.