A strong earthquake hit Japan's northern coast near the nuclear power plant crippled in the 2011 earthquake and tsunami. The earthquake early Saturday triggered a small tsunami and injured at least one person.

Japan's Meteorological Agency said the 6.8-magnitude quake struck 10 kilometres below the sea surface off the coast of Fukushima. The 4:22 a.m. quake shook buildings in Tokyo, about 193 kilometres southwest of the epicentre.

A 20-centimetre tsunami reached the coast of Ishinomaki Ayukawa and Ofunato, about 50 minutes after the quake. Smaller waves were observed at several other locations along the coast. Changes to the shoreline were not visible on television footages of NHK public broadcaster.

In Fukushima, a 68-year-old woman fell down the stairs and broke her leg, according to the prefectural police. No damage was reported.

All evacuation advisories lifted 2 hours later

Eight towns devastated by the tsunami three years ago, including Rikuzentakata, Higashi Matsushima and Otsuchi, issued evacuation advisories to thousands of households along the northern coast, along with schools and community centres.

All tsunami and evacuation advisories were lifted about two hours after the quake.

Fukushima Dai-ichi and two other nuclear power plants, along with other nuclear facilities along the coast, found no abnormalities, and their reactors and fuel storage pools are being cooled safely, according to the Nuclear Regulation Authority.

Tokyo Electric Power Co., which operates the Fukushima Dai-ichi plant, has instructed plant workers on night duty along the coast to retreat to higher grounds.

The March 2011 disaster killed about 19,000 people. That disaster also triggered multiple meltdowns at the Fukushima plant. More than 100,000 people are still unable to go home due to fear of radiation contamination from the plant.