A man from Greater Manchester has been arrested on suspicion of conspiracy to kidnap after police received reports of a group of men carrying a man into a car which was driven away.
The 19-year-old remained in police custody for questioning on Tuesday evening and hasn't been named.
Police in Bournemouth, Dorset, said as a major investigation was launched they have not yet identified the reported victim and 'are concerned for his welfare'. Five people have been arrested in total, Dorset Police said, with one, a 32-year-old woman, later released on bail pending further investigations.