A 6.8-magnitude earthquake struck off Japan's northeastern coast Friday, triggering a 50 cm (20 inch) tsunami warning that was lifted about 35 minutes later.

The epicenter of the quake, which hit at 2:36 pm, was off the coast of Fukushima, 20 km below Earth's surface, the same region where the massive 9.0 magnitude earthquake struck on March 11, followed by the devastating 30-meter tsunami, according to the Japan Meteorological Agency.

The agency said there was no damage from Fridays's quake and the tsunami advisory was lifted after no waves were sighted. Some highways were closed and high-speed bullet trains were halted after the quake, public broadcaster NHK said.

Friday's tremor was felt in Tokyo where buildings swayed mildly, according to local reports.

Tokyo Electric Power Co. said no problems were reported at its radiation monitoring posts at the crippled Fukushima Daiichi nuclear power plant, about 240 km (150 miles) northeast of Tokyo, or the nearby Daini plant, and cooling operations at the damaged reactors were continuing.

At the nuclear plant, some staff was temporarily evacuated immediately after the earthquake, according to Washington Post.

Tohoku Electric Power Company said there were no abnormalities at its Onagawa nuclear power plant, which was shut since the March disaster, according to Reuters.

Japan is frequently rocked by earthquakes as it sits on top of four tectonic plates. The latest quake comes when Japan is struggling to recover from the March disaster, whch killed more than 20,000 people.

The March quake triggered the world's worst nuclear crisis in 25 years at the Fukushima Daiichi plant as its cooling systems were knocked out, which led to meltdowns and radiation leaks that are yet to be plugged.

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