Six people have been arrested in London and Peterborough in relation to the human trafficking of more than 100 women, the Metropolitan police has said.
The arrests were made in relation to alleged sexual exploitation, controlling prostitution and money laundering offences.
A police spokesperson said 10 people were rescued during dawn raids following police visits to more than 15 brothels.
The Met and Hungarian Police carried out a joint investigation.
Scotland Yard said a Hungarian organized crime group had been advertising sexual services online.
During the investigation one of the alleged victims escaped from her traffickers and contacted police.
The crime group is also suspected of operating in other countries including Belgium, Austria and Germany.