A 6.8-magnitude earthquake struck central Japan on Saturday, according to the country's meteorological agency.
The quake struck at 10.08pm local time in the Nagano region, about 170km (105 miles) north-west of Tokyo, with an epicentre at a depth of 10km. The Japan Meteorological Agency said there was no threat of a tsunami.
Firefighters said there were several injuries and at least one collapsed building in the village of Hakuba, the Kyodo News Agency reported.
Japan's public broadcaster NHK reported that several people may be buried under collapsed buildings in Nagano Prefecture.
NHK also reported that some traffic was disrupted due to a landslide which caused a road block, with road and train authorities carrying out checks to ensure safety.
High-speed trains were also halted but there were no immediate reports of serious damage from the earthquake. Around 200 homes are believed to be without power.
The US Geological Survey recorded a lower earthquake intensity of 6.2 and its online ShakeMap estimated that strong tremors would have been felt near the epicentre, with a potential for light damage.
NHK quoted Tokyo Electric Power Company as saying that there was no damage to any of the seven nuclear reactors at the large Kashiwazaki-Kariwa plant in the neighbouring Niigata prefecture, as they have been offline since 2011.
Japan is affected by about a fifth of the world's powerful earthquakes every year, as it sits at the conjunction of several tectonic plates.
In March 2011, the country was hit by a 9.0-magnitude quake that triggered a massive tsunami, which in turn sparked the Fukushima nuclear disaster. Around 18,000 people died or went missing in the aftermath of the disaster.
Earlier today, China's Sichuan province was hit by a 5.8-magnitude earthquake.