A rollercoaster in Japan, said to be the world's fastest-accelerating, has closed indefinitely following reports that multiple riders suffered serious injuries.

The Fuji-Q Highland amusement park said four customers had broken bones on the "Do-Dodonpa" attraction between December 2020 and August 2021.

Others have reported sustaining neck, chest and bone fractures.
In a statement the park said the ride had closed "due to a safety overhaul".
However, it added that "the causal relationship between injuries and amusement machines has not yet been confirmed".

According to the regional government, the four incidents were among men and women in the 30-50 age range. All had "significant injuries", including a cervical fracture and a thoracic spine fracture.

A thoracic spine fracture can require up to three months in the hospital.
Despite the injuries occurring over an eight-month period between December and August, they were only reported to officials last week.
Sansei Technologies, the Osaka-based firm that built the rollercoaster, issued an apology to all the injured riders.

But the company cautioned that a connection between the injuries and the ride "is not confirmed" and said that they would now wait for the conclusion of an investigation by the regional government.

First opened in 2001, the ride was renovated in 2017 and goes from 0 to 180 km/h (112 mph) in just 1.56 seconds.

The park noted that the incidents are the first reports of injuries since the ride went into operation two decades ago.

Despite the impact of the coronavirus pandemic in Japan and a significant recent rise in cases, theme parks in the country have been open since June 2020.

However, Fuji-Q Highland is among the many parks that have sought to limit visitors, only reopening outdoor attractions.