Three strong earthquakes, of between 6.5 and 6.8 magnitude, have struck off the coast of the Canadian province of British Columbia, according to the United States Geological Survey.

All the quakes occurred in less than an hour on Sunday night.

There were no immediate reports of casualties or of any damage from the earthquakes.

A 6.6 magnitude quake struck first, at 10.39 pm local time.

The quake hit at a depth of 33 km, about 190 km southwest of Port Hardy, a town on the northeast end of Vancouver island.

A 6.8 magnitude quake and a 6.5 magnitude one occurred in succession shortly afterwards.

Geophysicist Amy Vaughan said that there were possibly some smaller quakes as well as some aftershocks.

Ms Vaughan added that the earthquakes were lightly felt onshore.

British Columbia sits in the North American portion of the Ring of Fire, an arc of volcanoes and fault lines in the Pacific Basin.

Its position means it is at risk of being hit by earthquakes.

The US National Tsunami Warning Center said that a tsunami is "not expected."

Additional reporting by agencies