A spokesperson from British Transport Police said they were called at just before 11.20am following a report of a person hit by a train.
They went on to say: “Officers from British Transport Police and Sussex Police attended the incident, alongside colleagues from the ambulance service.
“A man has been pronounced dead at the scene and officers are now working to identify the man and inform his family.
“The incident is not believed to be suspicious.”
Lines were blocked between Littlehampton and Brighton due to the incident, but have now been re-opened.
Disruption to the rail service in the area is expected until around 4pm.
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