A man is being held after a woman reported being attacked and an attempt made to pull her trousers down as she walked across a footbridge in Suffolk.
The victim, who is in her 30s, told police she was hit and knocked to the ground on the bridge at Oulton Broad South railway station on Tuesday night.
She said she then felt the man trying to pull her trousers down but managed to get free and run away, police said.
Officers were called and arrested the man a short time later.
He is in custody at Lowestoft Police Station where he will be interviewed by detectives.
Police are asking anyone who they saw a man or a woman walking, or the incident at 2230 BST, to come forward.