A 19-year-old man has been arrested in Birmingham under the Terrorism Act.
The teenager was detained by West Midlands Police officers
The man, who has not yet been named, was arrested in Gleave Road, Selly Oak at 0400 BST on Thursday.
He is currently being held at an unnamed police station, where he will be questioned by officers.
Police are understood to be conducting further inquiries in Selly Oak, where two men, aged 24 and 36, were also arrested in relation to alleged immigration matters.
According to the Home Office there have been 609 arrests under terrorism legislation between September 11, 2001 and 30 June 2004.
Of those people, 99 have been charged with terrorism-related offences, and 15 convicted.
Eight men - arrested in anti-terrorist raids two weeks ago - appeared before a judge at Belmarsh magistrates court in south-east London on Wednesday.
They were charged with conspiring to commit murder and conspiring to launch radioactive or chemical attacks. All were remanded in custody for a week.
An anti-terror police spokesman said the arrest in Birmingham was not related to this case.