TOKYO – A large earthquake shook a large area in eastern Japan with its epicenter off the coast of Fukushima late on Saturday evening, near which three nuclear reactors were melted down after a quake and tsunami almost 10 years ago.

No deaths from the quake had been reported by Sunday morning, Prime Minister Yoshihide Suga said. However, according to the state broadcaster NHK, more than 100 people were injured.

The quake left nearly one million households across the Fukushima area without power, forcing roads to be closed and trains to be suspended. While residents braced themselves for aftershocks, a landslide cut off part of a main artery through Fukushima Prefecture.

Japan’s weather service reported the magnitude of the quake at 7.3 versus its initial 7.1 rating, but said there was no risk of a tsunami.

A little less than a month before the 10th anniversary of the so-called Great Earthquake in eastern Japan and the Fukushima nuclear disaster, the quake struck an area that stretched from Hokkaido to the Chugoku region in western Japan.

Greater Tokyo felt the quake for about 30 seconds from 11:08 p.m., but the tremors were felt most in Fukushima and Miyagi.

The quake was a disturbing reminder of the far more powerful 8.9 magnitude earthquake and tsunami that devastated Japan in 2011, killing more than 16,000 people. After the subsequent nuclear disaster in Fukushima, 164,000 people fled or were evacuated from the vicinity of the plant.

In comments following a meeting on the Sunday morning quake, Mr Suga warned residents to be prepared for aftershocks and take precautionary measures.

“Please remain vigilant for the possibility of other similar sized earthquakes for the next week,” he said, adding, “Don’t be negligent.”

The quake on Saturday happened as Tokyo and nine other major prefectures are in a state of emergency to contain the coronavirus. Residents are encouraged to work from home and not go out at night, while restaurants and bars close at 8 a.m. each evening.

Japan is also preparing to host the Summer Olympics, which will be postponed for a year from 2020. The games are scheduled to open on July 23.

In response, the authorities are precisely mobilizing the nuclear power plants.

The prime minister’s office immediately set up a crisis management office, and Tokyo Electric Power Company, or Tepco, which maintains the disabled nuclear power plants, said they are checking their surveillance posts in Fukushima to make sure there are no radiation leaks.

Shortly after midnight, the public broadcaster NHK reported that Tepco had not found “no major anomalies” in any of the Dai-ichi reactors where the 2011 meltdown occurred, or at the Dai-ni plant in Fukushima a few miles away.

Early Sunday morning, Tepco said it found water in some of the pools that store spent fuel spilled on the pool decks in the reactors at both the Dai-ichi and Dai-ni plants. But Tepco said no water leaked outside of the reactors.

Tepco also reported that some small leaks from a tank filled with contaminated water had occurred on the Dai-ichi site, but the leak was contained in a small area.

The Kashiwazaki-Kariwa nuclear power plant on the west coast did not suffer any damage, reported NHK.

According to Katsunobu Kato, Chief Cabinet Secretary of Prime Minister Yoshihide Suga, around 950,000 households in the affected areas were without electricity. He said that two thermal power plants in Fukushima Prefecture had gone offline. Several high-speed trains were suspended. People in dozens of households have been evacuated to shelters in several cities in Fukushima.

In brief comments to reporters just before 2 a.m., Mr. Suga advised residents not to go outside and prepare for aftershocks.

Aftershocks: What the hours and days can hold before us.

Takashi Furumura, professor at the Tokyo University Earthquake Research Institute, warned in a lecture on NHK that a quake of this size could be followed by a quake of similar magnitude within two or three days.

The Japan Meteorological Agency said the epicenter of the quake was about 60 kilometers off the coast of Fukushima and about 34 miles deep. On land the strongest strength was 6 plus.

Speaking at a press conference, Meteorological Bureau official Noriko Kamaya said residents should be prepared for magnitude 6 aftershocks in the coming days. She described the Saturday night earthquake as an aftershock of the 2011 quake.

In Minami Soma, one of the villages in Fukushima evacuated after the 2011 nuclear disaster, NHK reported that violent tremors lasted about 30 seconds on Saturday.

Yu Miri, the author of Tokyo Ueno Station, winner of the National Book Award for Translated Literature, posted photos on Twitter of shabby bookshelves in her nearby house and the floors littered with books.

Kyodo News reported that 50 people were injured in the Fukushima and Miyagi areas of the east coast of Japan.

Japan has had a history of devastating earthquakes.

Around a dozen powerful earthquakes have struck Japan in the past decade, some of which triggered tsunamis and landslides that shook parts of the country and destroyed countless buildings.

In 2016, more than 40 people died after two earthquakes hit the southern island of Kyushu. The largest of the two recorded a magnitude of 7.0, close to the intensity of Saturday’s quake, and several died in fires and landslides in the mountainous area.

In 2018, tens and millions died in their homes after a powerful quake caused landslides on the north island of Hokkaido. This summer’s quake came just days after Japan’s largest typhoon in 25 years.

Makiko Inoue, Hisako Ueno, Hikari Hida and Elian Peltier contributed to the coverage.