Six of the suspects were from the West Midlands and one was from West Yorkshire, the West Midlands police said Friday in a statement.
The arrests under the Terrorism Act of 2000 followed a routine vehicle stop in South Yorkshire on Saturday, police said. Firearms, weapons and other material were found inside the vehicle, prompting police to trace and arrest the driver, passenger and other suspects.
The car had been impounded on suspicion of having no insurance when the weaponry was found, police said.
"As soon as the items were discovered in the impounded vehicle, our priority was to protect the public by pursuing and arresting those we believed to be involved." Detective Chief Superintendent Kenny Bell, said in the statement. "Our inquiries are ongoing."
The BBC reported that the arrests weren't tied to the Olympics or Thursday's arrests of six terror suspects in London.
All seven men were detained at a police station in the West Midlands.