More than 100 people were injured in the earthquake

Takashi Chiba, who was acting governor of Akita prefecture at the time of the quake, stepped down citing "personal reasons," prefecture spokesman Hideo Fujii said.

"I am extremely tired both mentally and physically and have lost confidence in my ability to do my job," Kyodo news agency quoted Mr Chiba as saying.

The deputy governor continued playing pachinko, a popular Japanese pinball-style game, for 45 minutes after the powerful quake struck, even though a chauffeur-driven car was waiting outside the pachinko parlour, according to Kyodo.

A local pressure group is understood to be also looking into how often Mr Chiba used government vehicles for his pachinko visits.

More than 100 people were injured in the quake, and seismologists said the magnitude seven earthquake would have caused much more damage if it had not been so far underground.

Residents in the northern city of Sendai described the tremors as strong and prolonged. The Japanese Meteorological Office said it was the country's strongest quake since March 2001.

Mr Chiba, 63, told local newspapers he had been killing time at the pachinko parlour while waiting for an acquaintance.

Pachinko can be highly addictive, and its players have caused controversy before.

In April 2002, an 11-month-old Japanese baby died in the back of her parents' car from dehydration after they left her for two and a half hours to play pachinko.