The suspects, who ranged in age from 17 to 28, had been under surveillance for weeks, security officials said.
Very few details have been released on what the suspects were planning. British officials say the raids were necessary to ensure public safety.
The men are accused of planning a large-scale terror attack on targets inside the United Kingdom. The suspects are thought to be British nationals with links to Bangladesh and Pakistan.
Police have up to 28 days to question the suspects before they must be charged or released.
The Associated Press contributed to this story.