A TSUNAMI warning has been issued for coastal areas of Alaska and parts of Canada following an 8.2-magnitude earthquake.
Residents of Anchorage – population 300,000 – are being urged to get to higher ground amid warnings of an "extraordinary threat to life or property".
The earthquake struck at a depth of 6.2 miles at 9.31am GMT, the US Geological Survey said.
A tsunami watch is also in place for the whole US West Coast and Hawaii.
The Anchorage Office of Emergency Management warned those living in coastal areas of Alaska and British Columbia: "If you are located in this coastal area, move inland to higher ground.
"Tsunami warnings mean that a tsunami with significant inundation is possible or is already occurring.
"Tsunamis are a series of waves dangerous many hours after initial arrival time. The first wave may not be the largest."
Warning sirens are also ringing out across Kodiak, located about 157 miles northwest of the tremor's epicentre.
Emily Russell, a local radio reporter, said tsunami sirens were ringing out through the town as residents made their way to higher ground.
Residents of Anchorage – Alaska's largest city located around 500 miles from the epicentre – said they were alerted to it by text messages.
Gordy Armstrong said: "You grow accustomed to riding out the occasional earthquakes living up here in Anchorage…that one was different.
"Shook the house pretty good and just kept going. Hope the people down south are alright."
Shaun Dyess wrote: "I’m here in anchorage Alaska. It was shaking for along time. Hope no one got hurt."
And JoLynn Lund tweeted: The #earthquake was enough to wake you. The #tsunami alert alarm gets you out of bed."
More to follow.
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