A powerful 7.3 magnitude earthquake struck off the coast of Fukushima in northern Japan on Wednesday evening, triggering a tsunami advisory and plunging more than 2 million homes in the Tokyo area into darkness.

The region is part of northern Japan that was devastated by a deadly 9.0 quake and tsunami 11 years ago that also caused nuclear plant meltdowns.

The Pacific Tsunami Warning Center said there was no longer a tsunami threat though the Japan Meteorological Agency kept its low risk advisory in place. NHK national television said tsunami waves of 20 centimeters (8 inches) already reached shore in one area.

The Tokyo Electric Power Company Holdings, which operates the Fukushima Daiichi nuclear plant where the cooling systems failed after the 2011 disaster, said workers found no abnormalities at the site, which was in the process of being decommissioned.

Chief Cabinet Secretary Hirokazu Matsuno told reporters that there were also no abnormalities at two other nuclear power plants in the area.

The Japan Meteorological Agency said the quake hit at 11:36 p.m. at a depth of 60 kilometers (36 miles) below the sea.

Japan's Air Self-Defense Force said it dispatched fighter jets from the Hyakuri base in Ibaraki prefecture, just south of Fukushima, for information gathering and damage assessment.

NHK said there were reports of fire, damage to buildings and falling rocks in Iitate town in Fukushima. There was no word on any casualties.

More than 2 million homes were without electricity in the Tokyo region serviced by TEPCO due to the quake, the utility said on its website. The quake shook large parts of eastern Japan, including Tokyo, where buildings swayed violently.

East Japan Railway Co. said most of its train services were suspended for safety checks.

Prime Minister Fumio Kishida told reporters that the government was assessing the extent of damage and promised to do its utmost for rescue and relief operations.

“Please first take action to save your life," Kishida tweeted.

Matsuno said there were a number of emergency calls and local authorities were scrambling to assess damage.

“We are doing our utmost in rescue operations and putting people's lives first,” he said.

He urged residents in the affected areas to use extra caution for possible major aftershocks for about a week.