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 / Updated  / Source: Reuters
By Henry Austin

An earthquake shook buildings and halted train lines in Tokyo early Monday, days after Japan's nuclear regulator green-lighted the restarting of atomic energy at a third plant.

The quake, with a preliminary magnitude of 5.6, was centered in Ibaraki prefecture just northeast of the country’s capital, the Japan Meteorological Agency said. There was no tsunami warning.

Narita airport closed both runways for checks shortly after the quake, but the capital's Haneda airport was operating as normal.

There were no immediate reports of damage or injuries, and no reports of abnormalities at any nuclear facilities.

But the quake is likely to reignite the debate about whether the country should use nuclear power in one of the world's most seismically active nations.

After the country was hit with a massive earthquake and tsunami that left nearly 20,000 people dead and set off meltdowns at the Fukushima Dai-ichi nuclear plant in 2011, opposition to the use of nuclear power grew.

In the aftermath of the disaster, all of Japan's 48 other nuclear reactors were shut down for inspection and upgrading.

Since then most public opinion polls have put opposition to nuclear restarts at about two-to-one over support. This is despite an average 20 percent rise in household electricity bills to cover the cost of imported fuel.

But last month Prime Minister Shinzo Abe's government proposed bringing nuclear energy back to account for 20-22 percent of the nation's electricity mix by 2030.

They see resuming nuclear power, which provided about a third of Japan's electricity supply before Fukushima, as the key to lifting the economy out of two decades of anemic growth.

Japan's nuclear regulator signed off on the basic safety of a reactor at the Ikata nuclear plant Wednesday, 434 miles west-southwest of Tokyo on Shikoku island.

Two other nuclear plants operated by Kansai Electric Power and Kyushu Electric Power have passed through the first stage of regulatory checks.

Reuters contributed to this report.