An earthquake with a preliminary magnitude of 5.1 shook northern Japan on Saturday, a Japanese government agency said, but there were no immediate reports of damage.

The quake, at 4:49 p.m. (3:49 a.m. EDT), was centered under the sea off Ibaraki prefecture, just north of the capital, Tokyo, where it was also felt.

TV pictures showed lamp posts shaking but there were no reports of injuries or damage.