A massive earthquake struck the northern Pacific Ocean on Wednesday, triggering fears of tsunami waves from Japan to Canada to Indonesia, officials said. The earthquake was magnitude 8.1, some 600 km northeast of Japan’s main northern island of Hokkaido, according to the Japan Meteorological Agency.The area where the quake hit is isolated, with the Russian-administered Kuril island chain the closest populated area. Japan issued warnings for all of its east coast from Tokyo north, saying that seismic waves of up to two meters could strike the shore. But the first tsunami known to hit the coast was a mere 40 cm. It struck the north-eastern Japanese town of Nemuro at 9.42 pm, 87 minutes after the earthquake. The agency downgraded the warnings to tsunami advisery on late Wednesday.

However, Japanese officials still warned that the threat was not over. In Tokyo, the government set up a special communication office to collect information about the tsunami. “The tsunami warnings and adviseries are still out there and the first tsunami waves are beginning to be observed. People need to remain cautious,” Takeshi Hachimine, a meteorological agency official, told a news conference.

Some 10,000 Russian inhabitants of the Kuril islands in far eastern Russia were taken to higher ground following the quake, Russian officials said, adding that there had so far been no reports of damage. The US Pacific Tsunami Warning Centre said the warning was in effect for both Russia and Japan along with the Pacific islands of Marcus, Wake and Midway.

It issued a tsunami watch for areas including Indonesia — which is still recovering from the devastating 2004 quake — along with Hawaii, the Philippines and Taiwan. “An earthquake of this size has the potential to generate a destructive tsunami that can strike coastlines in the region near the epicentre within minutes,” it said. The West Coast/Alaska Tsunami Warning Centre in Palmer, Alaska, issued a tsunami warning covering the areas from Sand Point, Alaska, to Attu, Alaska.

It said a tsunami watch was in effect for Washington state and British Columbia, as well as the area from Cape Flattery, Washington to Sand Point, Alaska. “At this time, this message is advisery only for other areas of California, Oregon and Washington,” it added. Japanese officials urged residents to head to higher ground, a warning passed on by local authorities. Hokkaido authorities said they were issuing mandatory evacuation orders for 10 municipalities.