The magnitude 5.7 quake hit Shizuoka prefecture, and authorities warn of possible strong aftershocks in coming days.

More than 20 people have been injured after a strong earthquake shook central Japan, shattering store windows and sending people fleeing buildings, according to local media and authorities.

The magnitude 5.7 quake struck at 1:04am local time on Sunday (16:00 GMT Saturday) at a depth of about 40km (25 miles) in western Shizuoka Prefecture, according to the Japan Meteorological Agency.

More than 20 people were injured in the Aichi and Shizuoka prefectures, the Kyodo news agency cited authorities as saying.

A wide area near Aichi Prefecture was affected, including the city of Hamamatsu, the ancient capitals of Kyoto and Nara, and the prefectures of Yamanashi, where Mount Fuji is located, and Gifu.

No tsunami warning was issued, Kyodo reported.

The quake was not felt in Tokyo, which is far from the epicentre.

Japanese television showed shattered shop windows and shards of glass scattered across streets. A bookstore was left with mounds of books that had fallen from the shelves.

Some of the injured had fallen on the stairs as they tried to flee, the Associated Press news agency reported.

Aftershock warnings

The meteorological agency warned people to be ready for possible strong quakes in the coming week, especially the next two to three days.

“Please be on the lookout for mudslides, falling rocks and the possible effects from rainfall,” agency official Ayataka Ebita told reporters.

He said no apparent change had been detected so far in the Nankai Trough, an underwater ocean trench where two major tectonic plates meet under parts of Japan, where scientists say a megaquake could occur.

Some local train services were suspended, while the Shinkansen bullet trains were running at slower speeds in affected areas as a precautionary measure.

Trains on the Tokaido Shinkansen line, which connects Tokyo and Osaka, were delayed between Shizuoka and Gifu-Hashima stations after safety checks, rail operator JR Central said.