Magnitude 7.8 earthquake strikes off the coast of Russia and Alaska

A powerful earthquake of magnitude 7.8 which hit Alaska is expected to cause tsunami waves, the US Pacific Tsunami Warning Centre says.

The quake struck in the northern Pacific Ocean between the tip of the Aleutian Islands and Russia's Kamchatka, according to the US Geological Survey which initially recorded it as 7.7.

It is expected to cause tsunami waves within 300 kilometres, according to the warning centre.

However, Civil Defence says there is no tusunami threat to New Zealand following the quake.

- AAP