A massive 8.8 magnitude earthquake off Russia's far eastern coast has triggered tsunami warnings across the Pacific.

The earthquake, which hit near Russia's Kamchatka Peninsula at about 11:25am local time on Wednesday (00:25 BST), is believed to be one of the most powerful ever recorded.

Around two million people were ordered to evacuate in Japan, Russia and Hawaii - but some warnings have since been downgraded.

Alerts were also issued in China, the Philippines, Indonesia, New Zealand and even as far as Peru and Mexico.

Videos have emerged showing large waves surging past buildings in the town of Severo-Kurilsk, Russia. Authorities said 4m (13ft) waves flooded the port and a fish processing facility, and vessels had been swept from their moorings. A power grid was also damaged in Russia's Sakhalin region.

In Japan, about 1.9 million people were asked to evacuate and authorities urged residents to reach higher ground. Initial waves reaching the country have been relatively small, but its meteorological agency said they could grow to 3m (9.8ft).

Japan's weather agency has since downgraded many of its tsunami alerts to advisories.

In Hawaii, officials first warned of possible 10ft waves, but the tsunami warning covering the island has also now been downgraded to an advisory level, the Pacific Tsunami Warning Center said.

This means there is the potential of strong waves, minor flooding and strong currents, but that a major tsunami is not expected to hit. Those evacuated may return home, Stephen Logan, the Hawaii Emergency Management Agency's director, said.

So far, the damage does not appear to be as bad as first feared - though tsunami waves are continuing across the Pacific ocean.

"Even now, scientists are running new models to try to refine initial forecasts," Chris Goldfinger, Professor of Marine Geology at Oregon State University told BBC Breakfast.

"Each country, each port, and each coastline will experience a very site-specific response. Some places it will be fairly minimal, some quite serious."

He said the extent of the impact depends largely on the path of energy radiating from Russia's Kamchatka peninsula. Areas directly in line with that energy - roughly southeast from the epicentre - are expected to be most affected.

He said it takes about "eight to nine hours" for a tsunami from Kamchatka to reach the US west coast.

The earthquake struck at about 11:25am local time (00:25am BST) on Wednesday.

Tsunami waves hit parts of North America's west coast at around 12.20am local time (09.20am BST).

The waves are then expected to hit areas including the Port of Tacoma in Washington at 2.20am (11.20am BST) and Nome, Alaska at 03.20am (12.20pm BST).

"A good rule of thumb for tsunami waves is that they travel at about the speed of a jet plane," Helen Janiszewski, assistant professor in geophysics and tectonics division at the University of Hawaii, told the BBC.

"So if you think of how long it would take to travel by plane from one place to another, that is how long it takes for waves to travel from the quake epicentre to hit elsewhere," she said.

The US Geological Survey said the earthquake was relatively shallow - striking at a depth of 20.7 km (12 miles), and centred 119 km east-southeast of Petropavlovsk-Kamchatsky.

It was initially recorded as an 8.0 magnitude earthquake but later revised upwards. A series of strong aftershocks have also been recorded.

It is tied for the sixth most severe quake in history, with the 2010 earthquake in Biobío, Chile, and the 1906 earthquake in Esmeraldas, Ecuador.

The fifth most severe earthquake was also in Kamchatka Krai, Russia, in 1952. It was "the world's first recorded magnitude 9 earthquake".

By comparison, the 2004 Indian Ocean earthquake and tsunami - which killed over 227,000 people - was a 9.2-9.3 magnitude earthquake.

That hit approximately 160km off the western coast of Sumatra, Indonesia - a densely populated area. Russia's Kamchatka Peninsula has very low population density.