A man has died in a freak accident on a double-decker bus in the UK.

The passenger, aged in his 30s, was travelling through Oxford in England on October 26 when he fell down the stairs and suffered serious injuries.

The man was treated on the bus before he was rushed to a nearby hospital. However, he died five days later on October 31.

A police spokesperson confirmed an investigation into the fatal incident is underway and while his death is being treated as unexplained, it has not been deemed suspicious.

The bus company — Oxford Bus Company — revealed they are assisting police with the investigation.

“A passenger on board one of our vehicles received emergency medical treatment after an incident in which no one else was involved,” a spokesperson said.

“Following medical assistance on the vehicle in Oxford the passenger was taken to the John Radcliffe Hospital by ambulance.

“We are assisting the emergency services with their inquiries and have given CCTV footage to the police.

“Our thoughts and condolences are with the deceased’s family and friends at this incredibly difficult time.”