A man was arrested by guards on board the Viking Line ferry MS Isabella. He was met by police on the dockside when the ferry arrived at the Södermalm terminal in Stockholm from Finland on Sunday morning.
A spokesman for Stockholm Police said he could not confirm reports that the incident had been a gang rape.
“That is not the information that we have,” said Evert Norberg, commander in Södermalm.
“It could be the case that the man was part of a gang,” he added.
The woman was taken to hospital in Stockholm for examination and treatment.