Six Everton fans, including a 15-year-old boy, have been arrested in connection with an attack outside a pub in north London.
Scotland Yard carried out early morning raids at seven addresses across Liverpool, Wirral and Warrington.
The suspects are aged between 15 and 54.
Police said a 24-year-old man was also arrested on suspicion of violent disorder in Crawley, Sussex.
The arrests followed clashes between a group of about 30 Everton supporters and a smaller group of Newcastle United and Hull City fans.
'Wealth of images'
They were drinking outside Millers pub in Islington in the early evening on 16 May.
All three teams had played matches in the capital.
A 51-year-old man was taken to hospital with a head injury.
Merseyside Police helped to identify some of the suspects from CCTV and mobile phone footage.
Scotland Yard said the "wealth of images" helped other forces identify and track down suspects.
Det Ch Ins Andy Barnes, of Operation Arrowtip, which investigates football-related crime and disorder in London, said: "Violence amongst supporters has no place in football; be it before, during or after a match.
"These investigations show that no matter where you are from, or who you support, UK policing will work together to identify suspects and take action against them."
The seven people arrested have been released on bail pending further inquiries.
Three men arrested shortly after the clash, including a 52-year-old man arrested on suspicion of three counts of assault and two men arrested on suspicion of affray, have also been bailed pending further inquiries.