Three people are confirmed dead following the magnitude-7.1 aftershock that rattled Japan, but no new damage was reported at the stricken Fukushima Daiichi nuclear power plant.
Thursday's aftershock was the strongest since the devastating quake and tsunami that flattened the country's northeastern coast last month.
The latest aftershock has also injured over a hundred people, authorities said.
Officials at the tsunami-ravaged Fukushima plant said there was no immediate sign of new problems.
"Local power plants were designed to sustain 7.9 earthquakes. So this kind of earthquake - a 7.1 or 7.4 - they sustained [it] without damage," Jasmina Vujic, professor of nuclear engineering at the University of California, Berkeley, told Al Jazeera.
"What I suspect is simply that there was splashing of water in spent fuel pools and water in the spent fuel pool is really mildly radioactive so if there were splashes it is inside of the plant. So I don't see any ways the level of radiation might have increased."
However, Japan's nuclear safety agency said workers there had retreated to a quake-resistant shelter in the complex. No one there was injured.
Al Jazeera's Marga Ortigas, reporting from Mizusawa in northeast Japan, said there had been reports of gas leaks and power cuts following the quake.
"Some train tracks have also been displaced and people were trapped in lifts. But Japanese officials have said that they do not expect further damage," she said.