|This was the 76th aftershock since the devastating March 11 quake and tsunami [Reuters]
A strong earthquake with a magnitude of 7.1 hit Japan's northeastern coast, an area still recovering from a devastating quake and tsunami that hit the island nation four months ago.
Workers at the crippled Fukushima nuclear power plant were evacuated on Sunday after an alert for a half-metre tsunami was issued by the Japan Meteorological Agency.
Officials said there were no reports of abnormalities at the Fukushima plant caused by Sunday's quake. Airports in the area were also functioning normally.
NHK, a Japanese broadcaster, reported a small tsunami of 10cm along the northeast coast, while residents in the coastal areas were warned to evacuate.
There were no immediate reports of injuries or damage from the quake, officials said.
Al Jazeera's Harry Fawcett said this was the 76th aftershock of more than 7.0 magnitude since the March 11 earthquake and tsunami that left nearly 23,000 dead or missing and triggered a radiation crisis at a badly damaged facility in Fukushima.
"There is still a great deal of geological activity going on and people are still worried about bigger [aftershocks] coming ... but the cooling system at Fukushima, we were told, carried on uninterrupted by this earthquake," Fawcett reported from Nagoya, a city located approximately 400km east of Tokyo, the capital.
All of the workers at Fukushima had been evacuated to higher ground, adding that there was no sign of any immediate further damage at the nuclear plant where workers have been struggling to build a cooling system to stabilize the reactors, Tokyo Electric Power said.
Tokyo Electric said it would be monitoring a massive barge moored just offshore from the Fukushima nuclear power plant that has been used as a temporary storage depot for radiated water for any damage.
Dozens of strong aftershocks have been felt since the March 11 disaster, which measured a 9.0 magnitude and was the strongest in Japanese history.
Sunday's quake registered 4 on the Japanese scale of 7, meaning it was felt as moderately strong.
The extent of damage from the March quake and tsunami, however, has left many buildings in the area structurally weak with seawalls destroyed, making the region more vulnerable to relatively weaker quakes.
The US Geological Survey initially estimated the Sunday's quake at magnitude 7.3, but then revised that estimate down to a 7.