A magnitude 7.9 earthquake hit the Gulf of Alaska in the early hours of Tuesday, prompting warnings of a possible tsunami down the west coast of North America.

The warnings were however cancelled after a few hours. 

Emergency sirens sounded in Kodiak, a town of 6,100 people on Alaska's Kodiak Island, one of the closest settlements to the epicenter.

"This is a tsunami warning. This is not a drill. Please get out to higher ground," said the announcer on local public radio station KMXT. "If you are on the flats, get up on one of the hills ... Just go high."

There were no immediate reports of damage or injury.

The quake, initially measured at magnitude 8.2, hit around 250 km (160 miles) southeast of Chiniak, Alaska at a depth of 25 km at 12:31 a.m. (0931 GMT), the US Geological Survey said.

"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," the Anchorage Office of Emergency Management said in a warning for Alaska and British Columbia.

"Based on all available data a tsunami may have been generated by this earthquake that could be destructive on coastal areas even far from the epicenter," the Pacific Tsunami Warning Center said.

An initial tsunami watch for Hawaii was cancelled.

Japan's meteorological agency said it was monitoring the situation but did not issue a tsunami alert.

The earthquake was so powerful, it was even picked up by the recorder of the Seismic Monitoring and Research Group at the University of Malta.