The largest earthquake since records began hit northern Japan at about quarter to three local time, just as the rush hour was about to start. BBC News has ongoing live coverage.
The tremor, measured at 8.9 by the US Geological Survey, hit at 1446 local time (0546 GMT) at a depth of about 24km.
A tsunami warning was extended across the Pacific to North and South America.
The Red Cross in Geneva warned that the tsunami waves could be higher than some Pacific islands, Reuters news agency said.
Coastal areas in the Philippines, Hawaii and other Pacific islands were evacuated ahead of the tsunami’s expected arrival.
New Zealand later downgraded its alert to a marine threat, meaning strong and unusual currents were expected.
