The warning was issued after a magnitude 7.3 quake struck offshore Friday, swaying buildings across much of Japan.
There were no immediate reports of serious damage but several people were reportedly hurt. Ishinomaki, a city in Miyagi, reported that a tsunami of three feet hit about 45 minutes after the quake.
Shortly before the earthquake struck, NHK television broke off regular programming to warn that a strong quake was due to hit.
Afterward, the announcer repeatedly urged all near the coast to flee to higher ground.
Tokyo Electric Power says there have been no problems at any of its nuclear plants.
(Copyright 2012 by The Associated Press. All Rights Reserved.)