Tokyo: A 5.4 magnitude earthquake shook central Japan on Thursday, seismologists said, injuring several people and causing cracks in a 16th-century samurai castle listed as a national treasure.

The quake hit at 8:16 am with the shallow focus located in Nagano prefecture, some 180 kilometres northwest of Tokyo, an agency in Japan said. It was followed by smaller aftershocks.

The tremor damaged Matsumoto Castle in Nagano, causing cracks in the inner walls of a tower built in the late 16th century, according to a municipal official.

Television footage showed fallen concrete bricks and roof tiles in the area.

Public broadcaster NHK said the morning tremor injured nine people, including a woman who fell off her bed.