Hawaii scrambled to evacuate locals and tourists from the coastline late on Thursday after a massive earthquake off Japan triggered a tsunami alert, officials on the Pacific island state said.
"We have about four hours to clear the shorelines," said John Cummings of the Honolulu Department of Emergency Management. "This looks like this will be a very serious event."
Warning sirens went off at 9.59 p.m. (0759 GMT Friday) and were to go off every hour on the hour afterwards. The first waves were expected to hit Hawaii around 2.55 am.
Authorities were arranging buses to evacuate residents and trying to open evacuation centers.
The pacific tsunami warning center, based in Ewa Beach, West of Honolulu, issued a widespread warning extending across virtually the entire Pacific Ocean, including Australia, Antarctica and South America.
Hawaii is some 4,000 miles East of the epicenter of Friday's earthquake.