A 7.8-magnitude earthquake struck off the Alaskan peninsula, triggering a tsunami warning for areas within 200 miles (300 kilometers) of the epicenter.
The shallow quake hit at 0612 GMT Wednesday about 500 miles southwest of Anchorage, and around 60 miles south-southeast of the remote settlement of Perryville, the US Geological Survey said.
"Based on the preliminary earthquake parameters ... hazardous tsunami waves are possible for coasts located within 300 km of the earthquake epicenter," the Pacific Tsunami Warning Center said.
A tsunami warning was in effect for the Alaskan peninsula and south Alaska.
Residents in tsunami warning areas were advised to move inland or to higher ground.
"For other US and Canadian Pacific coasts in North America, the level of tsunami danger is being evaluated."
The quake was felt hundreds of miles away.
"Bed and curtains were going. Felt like a very long quake!" one witness in Homer, Alaska, 400 miles from the epicenter, said on the quake monitoring website msc-csem.org.
It was followed by several aftershocks, the strongest measuring 5.7.
There were no immediate reports of damage or casualties.
The tremor appeared to be a subduction zone quake, where two tectonic plates converge, a seismologist said.
"It's the interface, the plate boundary between where the Pacific plate thrusts underneath North America. A very standard type of earthquake in this area," Mike West from the Alaska Volcano Observatory told Alaska Public Media.
Alaska is part of the seismically active Pacific Ring of Fire.
The US state was hit by a 9.2-magnitude earthquake in March 1964, the strongest ever recorded in North America. It devastated Anchorage and unleashed a tsunami that slammed the Gulf of Alaska, the US west coast, and Hawaii.
More than 250 people were killed by the quake and the tsunami.
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