A massive 7.8 magnitude earthquake has set off tsunami alerts in Alaska, Hawaii, and throughout the Pacific Ocean.

The quake struck near the Petropavlovsk-Kamchatsky region, off Russia's east coast Thursday at 2:58pm ET.

The National Oceanic and Atmospheric Administration's tsunami warning system has announced that Hawaii is officially under threat from dangerous waves triggered by the earthquake.

Two tsunami watches have been issued for Alaska's Aleutian Islands, which is the closest US territory to Thursday's eruption.

This advisory in Alaska covered an area from Attu to the Amchitka Pass, which are 125 miles west of Adak, Alaska.

People in these areas should avoid beaches, harbors, and low-lying coastal areas and stay alert for updates.

Meanwhile, a tsunami with waves one to three feet is expected to reach Hawaii.

However, the warning by NOAA is only an advisory-level alert at the moment, meaning minor waves or strong currents could occur, but widespread flooding is unlikely.

The earthquake (blue dot) struck near Russia's Petropavlovsk-Kamchatsky region at 2:58pm ET

In Russia, locals near the epicenter are under higher state of alert, as the tsunami warning system expects waves between three and 10 feet to strike.

This could cause more significant coastal flooding or damage, especially in low-lying areas.

The Kamchatka Peninsula has been repeatedly hit by major earthquakes this summer, include a magnitude 7.4 earthquake on September 13 and a devastating magnitude 8.8 earthquake that occurred on July 29.

Millions were placed under tsunami advisories after the July quake, including residents in Japan, Hawaii, and the US West Coast.

The US Geological Survey (USGS) called Thursday's 7.8 earthquake a giant aftershock of the larger quake that struck on July 29. It's the largest recorded aftershock linked to that event near Russia's coast.

USGS added that the major quake was triggered by a type of movement called reverse faulting, where two massive pieces of the Earth's crust push against each other.

In this area, the Pacific Plate has been sliding under the North American Plate at a speed of about three inches per year.

This movement happens along a huge underground boundary called the Kuril-Kamchatka subduction zone.

A 7.8 magnitude earthquake has struck near Russia's east coast, triggering tsunami warnings in Alaska and Hawaii (Stock Image)

Four additional earthquakes have already struck the region since the 7.8 magnitude quake struck, all of them registering over 4.6 in magnitude.

Millions under tsunami threat as 7.8 earthquake strikes the Pacific