WASHINGTON (AFP) - A 7.8-magnitude earthquake struck off the Alaskan peninsula, triggering a brief tsunami warning for areas within 300km of the epicentre.
Sirens blared as residents were warned to move inland or to higher ground, reports said.
The shallow quake hit at 0612 GMT Wednesday about 800km south-west of Anchorage, and around 96km 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 300km of the earthquake epicentre," the Pacific Tsunami Warning Centre said.
A tsunami warning for the Alaskan peninsula and south Alaska was later cancelled after only small waves were recorded.
Warning sirens were sounded in Kodiak, the main city on Kodiak island, and several thousand people were evacuating lower lying areas, Sergeant Daniel Blizzard, with the Alaska State Troopers, told 11 KTVA News.
"People are pretty concerned especially with an earthquake that big that close to Kodiak," he said. "The last one, there was no wave whatsoever. This time, we're not sure there is a wave, but we are preparing like there is one," Sergeant Blizzard said.
The first place predicted to see a tsunami wave, Sandy Point, had so far reported only "a very small wave," Mr James Gridley, director of National Tsunami Warning Centre in Palmer, told Alaska Public Media (APM).
"We're not expecting a massive wave anywhere," he said.
The quake however, was felt hundreds of kilometres away.
"Bed and curtains were going. Felt like a very long quake!" one witness in Homer, Alaska, 643km from the epicentre, 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," Mr Mike West from the Alaska Volcano Observatory told Alaska Public Media.
Alaska is part of the seismically active Pacific Ring of Fire.
Alaska 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.