Four men have been arrested on suspicion of travelling to Pakistan to undertake terrorist training and of raising funds for terrorist purposes.
They were arrested under the Terrorism Act today as part of a major ongoing investigation, police said.
Officers from the West Midlands Counter Terrorism Unit detained the men at their homes in the Sparkhill area of Birmingham in the early hours of the morning.
A police spokesman said the suspects, aged between 19 and 24, had been arrested as part of Operation Pitsford, a large-scale inquiry which has already seen eight other people charged with a variety of offences.
'Today's arrests were pre-planned and not made in response to any immediate threat to public safety,' the spokesman said.
Officers were unarmed during the raids, he added, and detectives have an initial 48 hours to question the suspects before charging, releasing or applying for a warrant of further detention.
Eight people arrested in September have already been charged in connection with the investigation and seven of them are currently on remand after appearing in court.
Six men and a woman were arrested in MI5-backed raids in 14 addresses in various areas of Birmingham in September.
Terror allegations: An artist's court sketch of Mohammed Rizwan, Bahader Ali, Ifran Nasser, Rahin Ahmed, Ifran Khalid and Ashik Ali when they appeared in West London Magistrates’ Court charged with terrorism offences #
The six later appeared at West London Magistrates’ Court charged with terrorism offences, including a suspected suicide bombing campaign.
Irfan Nasser, 30, Irfan Khalid, 26, Ashik Ali, 26, Rahin Ahmed, 25, Mohammed Rizwan, 32, and Bahader Ali, 28.
The charges included stating an intention to be a suicide bomber, preparing for an act of terrorism and raising money to send people to training camps in Pakistan. #
A seventh man, Mujahid Hussain, 20, was later accused of helping the six.