DCI Adam Lowe said:
"These arrests are part of an investigation into rape and serious sexual assault carried out by a group of men in Newham and the wider east London area. Our enquiries continue.
"I would urge anyone who has been a victim of this type of offence or who believes they have any information to please contact police on 020 8217 6531, or Crimestoppers on 0800 555 111."
Eight men have been arrested on suspicion of raping a young teenage girl, after dawn raids at several addresses in East London and Hertfordshire.
Five 23-year-olds, two 24-year-olds and one 21-year-old are being held in custody at a police station.
Officers from the Met's Sapphire Command are investigating alleged offences that took place between May and November 2012.