Tokyo: A powerful earthquake rocked Japan's northernmost main island of Hokkaido early on Thursday morning, triggering landslides that crushed homes, knocking out power and forcing a nuclear power plant to switch to a backup generator.

The magnitude 6.7 earthquake struck southern Hokkaido at 3:08am at a depth of 40 kilometres, Japan's Meteorological Agency said. The epicenter was east of the city of Tomakomai but the shaking buckled roads and damaged homes in Hokkaido's prefectural capital of Sapporo, with a population of 1.9 million.

Police search for missing persons around houses destroyed by a landslide. Credit:AP

Chief Cabinet Secretary Yoshihide Suga told a news conference that two people had been confirmed dead. He did not give details.

Japan is used to dealing with disasters, but the past few months have brought a string of calamities. The quake came on the heels of a typhoon that wreaked havoc in western Japan, leaving the main airport near Osaka and Kobe closed after a tanker rammed a bridge connecting the facility to the mainland. The summer also brought devastating floods from torrential rains in Hiroshima and deadly hot temperatures across the country.