The shallow earthquake on Wednesday damaged buildings and injured several people in the remote Russian region, while much of Japan's eastern seaboard - devastated by a 9.0 magnitude earthquake and tsunami in 2011 - was ordered to evacuate.
Tsunami waves struck parts of Kamchatka, partially flooding the port and a fish processing plant in the town of Severo-Kurilsk and sweeping vessels from their moorings, regional officials and Russia's emergency ministry said.
"Today's earthquake was serious and the strongest in decades of tremors," Kamchatka Governor Vladimir Solodov said in a video posted on the Telegram messaging app.
Russian scientists said it was the most powerful quake to hit the region since 1952.
In Hawaii, coastal residents were told to get to high ground or the fourth floor or above of buildings, and the US Coast Guard ordered ships out of harbours as the tsunami approached.
"Take Action! Destructive tsunami waves expected," the Honolulu Department of Emergency Management said on X.
The Pacific Tsunami Warning Center said waves up to 1.7m were affecting the Hawaiian islands.
State Governor Josh Green had earlier said no waves of consequence had hit Hawaii but all flights in and out of Maui had been cancelled.
The US Geological Survey said the shallow earthquake was at a depth of 19.3km and centred 119km east-southeast of Petropavlovsk-Kamchatsky.
It revised the magnitude up from 8.0 earlier, and reported strong aftershocks up to 6.9.
Tsunami alarms sounded in towns across Japan's Pacific coast and evacuation orders were issued for tens of thousands of people.
Workers fled the stricken Fukushima nuclear plant, where a meltdown following the 2011 tsunami caused a radioactive disaster, operator TEPCO said.
Footage on public broadcaster NHK showed scores of people on the northern island of Hokkaido on the roof of a building, sheltering under tents from the beating sun, as fishing boats left harbours to avoid potential damage from the incoming waves.
Broadcaster Asahi TV reported a 58-year-old woman died when her car fell off a cliff while she was evacuating in central Japan's Mie prefecture.
Three tsunami waves were recorded in Japan, the largest of 1.3m, officials said.
Japan's government said no injuries or damage were reported, or irregularities at any nuclear plants.
The US Tsunami Warning System also warned of "hazardous tsunami waves" spreading across the Pacific.
Waves reaching more than 3m were possible along some coasts of Russia, the northern Hawaiian islands and Ecuador, while waves of 1-3m were possible in countries including Japan, Hawaii, Chile and the Solomon Islands, it said.
"Due to a massive earthquake that occurred in the Pacific Ocean, a Tsunami Warning is in effect for those living in Hawaii," US President Donald Trump said in a social media post.
Russia's emergency services ministry said on Telegram that a kindergarten was damaged but most buildings withstood the quake.
No serious injuries or fatalities were reported.
Several people in Kamchatka sought medical assistance following the quake, Oleg Melnikov, regional health minister, told Russia's TASS state news agency.
In Severo-Kurilsk in the northern Kuril islands, south of Kamchatka, tsunami waves exceeded 3m, with the largest up to 5m, Russia's RIA news agency reported.
Alexander Ovsyannikov, the town's mayor, said four tsunami waves had passed.
Power to the Sakhalin region was cut off due to damage to the electricity grid, RIA said, citing the regional governor.
"Aftershocks are currently ongoing ... Their intensity will remain fairly high. However, stronger tremors are not expected in the near future," said Danila Chebrov, director of the Kamchatka Branch of the Geophysical Service, on Telegram.
