The Fire and Disaster Management Agency said seven people were injured in Miyagi prefecture, including two elderly women — one who was banged in the head by a door and the other who was hit in the shoulder by furniture. In neighbouring Iwate prefecture, a woman in her 50s fell and cut her mouth.
The strong temblor caused a temporary blackout in some areas and suspended bullet train services in the area, according to the East Japan Railway Co.
The Nuclear Regulation Authority said no abnormalities have been detected at nuclear power plants in the region, including the Fukushima Daiichi nuclear plant, which suffered meltdowns in the 2011 quake and tsunami.
Akira Wakimoto, a crisis management official in Tome town in Miyagi prefecture, said he was in his apartment when the quake struck, and felt his room shake for a long time.
In a coastal city of Ofunato, Shotaro Suzuki, a hotel employee, said there was a temporary blackout and elevators stopped briefly, but power has been restored and there were no other problems.
"Our guests seemed worried at first, but they have all returned to their rooms, and our facility seems fine," Suzuki told NHK.
In mid-February, another powerful quake in the region killed one person and left more than 180 injured, though most injuries were minor. The quake damaged roads, train lines and thousands of houses. It also caused minor damage to the Fukushima Daiichi nuclear plant.
A Japan Meteorological Agency spokesperson, Noriko Kamaya, said in a news conference that Saturday's quake is considered an aftershock of the 9.0 magnitude quake in 2011. Kamaya urged people to use caution and stay away from the coastline due to possible high waves.