Four men have been arrested in Cardiff by detectives investigating slavery and kidnap allegations, Gwent Police said.
An operation involving three police forces saw warrants executed at five addresses in Bristol and Cardiff this morning. Four men from the Rumney area of the Welsh capital were arrested.
Police working on Operation Imperial are probing alleged offences of slavery, forced labour, false imprisonment, kidnap and assault.
Lead officer Detective Superintendent Paul Griffiths said: "The alleged offences we are investigating are extremely serious and we would urge anyone with any information which could assist to contact the Imperial team directly."