File photo - A screen showing a seismograph reading of an earthquake.

A powerful 6.0-magnitude quake rumbled off the coast of Alaska early on Thursday, according to the US Geological Survey, but there were no immediate reports of casualties or damage.

The epicentre of the quake was 102 kilometres from Craig, Alaska and more than 1 000 kilometres from Vancouver, in the Canadian province of British Columbia, the USGS said.

The West Coast and Alaska Tsunami Warning Centre said there was no risk of the earthquake generating a tsunami.

An even larger 7.5-magnitude quake struck off Alaska in the same area earlier this month, generating a local tsunami and rattling homes as far away as the state capital Juneau, about 330 kilometres away.

The January 5 temblor also caused no casualties or damage. - AFP