A tsunami alert for Alaska and British Columbia has been issued following a huge 8.2-magnitude earthquake.

Much of the US West Coast is also under tsunami watch after the earthquake struck 175 miles south east of Alaska's Kodiak Island on Tuesday.

Warning messages from the National Weather Service urged people in Alaska to move inland or find high ground.

Text messages warned people on the island of tsunami danger along its coast.

People reported on Twitter being woken by the ground shaking and tsunami alert sirens sounding.

Residents as far as 300 miles north of Kodiak in Anchorage - Alaska's largest city - reported feeling strong shakes when the earthquake hit.