Japan on Tuesday struggled to assess the full extent of damage from an earthquake that struck its west coast, killing at least eight people, wrecking buildings and roads and knocking out power to swathes of homes in freezing temperatures.

The quake with a preliminary magnitude of 7.6 struck in the middle of the afternoon on Monday, prompting residents in some coastal areas to flee to higher ground as tsunami waves about 1 metre hit Japan's western seaboard.

Thousands of army personnel, firefighters and police officers from across the country have been dispatched to the worst-hit area in the relatively remote Noto peninsula.

However, rescue efforts have been hindered by badly damaged and blocked roads and one of the area's airports has been forced to close due to runway cracks.

Many rail services and flights into the area have also been suspended.

"The search and rescue of those impacted by the quake is a battle against time," Prime Minister Fumio Kishida said during an emergency disaster meeting on Tuesday.

Kishida said rescuers were finding it very difficult to reach the northern tip of the Noto peninsula due to wrecked roads, and that helicopter surveys had discovered many fires and widespread damage to buildings and infrastructure.

Public broadcaster NHK said eight deaths had been reported in the hard-hit town of Wajima near the quake's epicentre, while in nearby Suzu some doctors were unable to reach a hospital that was relying on a backup generator for power.

More than 90 tremors have been detected since the quake first hit on Monday, according to the Japan Meteorological Agency. The agency has warned more strong shocks could hit in coming days. (Reuters)