Office items are seen scattered on the floor of Kyodo News' Hakodate bureau in Hakodate, Hokkaido, shortly before midnight December 8, after a powerful earthquake struck the region. Kyodo/VNA Photo

TOKYO — A powerful quake with a preliminary magnitude of 7.5 struck northeastern Japan late Monday night, with the weather agency issuing a tsunami warning for coastal areas of Hokkaido as well as Aomori and Iwate prefectures before lifting it hours later.

The Japan Meteorological Agency also said the quake, which occurred at 11:15pm off Aomori's Pacific coast at a depth of 54 kilometers, raises the chance of a quake of a similar or even larger magnitude hitting the same area within the coming several days.

It is the first time the agency has issued such an alert for the coastal regions of Hokkaido and the Sanriku coast, which extends from Aomori through Iwate and Miyagi prefectures.

The Cabinet Office called on the public to maintain special readiness for at least a week, such as by keeping an emergency supply kit within reach so they can evacuate at a moment's notice if necessary.

The quake occurred in an area along the trench running off the coast of Hokkaido and northeastern Japan, where the government warns of major quakes caused by the Pacific plate subducting beneath the Honshu main island, according to the agency.

The M9.0 megaquake in 2011, which left nearly 20,000 people dead and over 2,500 missing and triggered the Fukushima nuclear disaster, also occurred off northeastern Japan.

The agency, which revised the magnitude from the initially reported 7.2, warned of tsunami of up to 3m following the quake. The highest tsunami observed was about 70cm in Iwate.

Three and a half hours after the quake struck, the tsunami warning was downgraded to an advisory. At 6:20am on Tuesday, the advisory was lifted.

The quake logged an upper 6 on the Japanese seismic intensity scale of 7 in parts of Aomori. It was felt in central Tokyo.

A special weather agency alert for a massive quake along the trench off the Pacific coast of northeastern Japan is issued following an earthquake when, after careful analysis, it is found to have had a magnitude of 7.0 or greater.

The agency assesses there is a one-in-100 chance that an M8 quake or greater could occur within seven days. But even when such an alert is in effect, the authorities do not call on the public to evacuate in preparation.

Prime Minister Sanae Takaichi, speaking to media at the prime minister's office, urge the public to heed information released by authorities over the next week and be ready to flee as soon as they feel the ground shake.

Chief Cabinet Secretary Minoru Kihara and Defense Minister Shinjiro Koizumi separately briefed reporters on the government's all-hands-on-deck response to the quake, saying rescue efforts were foremost in their minds.

In Aomori and Hokkaido, there have been reports of more than 10 injuries, including at least one serious case in Hokkaido's Hidaka, with no fatalities so far. The Aomori prefectural government said that around 2,700 homes were left without power.

No abnormalities have been reported by nuclear plants in Hokkaido or the northeastern prefectures of Aomori, Miyagi and Fukushima. The government also confirmed there were no abnormalities at a nuclear fuel reprocessing plant in Rokkasho, a Pacific coastal village in Aomori Prefecture.

Tohoku Shinkansen bullet train services have been halted between Fukushima and Shin-Aomori stations, operator JR East said. A bullet train carrying 94 passengers was briefly stranded in Aomori.

People awoken by the late-night temblor recalled the terror they experienced while trying to seek safety in subzero temperatures outside.

"I was asleep when shaking began as if I suddenly got hit from beneath. After that, shaking continued both vertically and laterally for a long time," said a man in his 40s in Hachinohe, Aomori Prefecture.

A 75-year-old woman in Kamaishi, Iwate Prefecture, said she was about to go to sleep when the quake hit. She took shelter on higher ground in a car driven by her daughter.

"I debated whether I should leave. I was afraid of a bear popping up, my husband needs care and we have a cat," she said.

Coastal areas in Aomori and Iwate saw the mercury fall below 5 C late Monday night. A 27-year-old municipal worker in Kuji, Iwate Prefecture, described ice on the windshield of the car he used to evacuate.

The Kyodo News bureau in Hakodate, Hokkaido, was left in disarray after the quake, with a steel bookshelf tipped over and files strewn across the floor. KYODO