Metropolitan Police say two men and a woman were arrested today morning in East London. Another man was arrested in Lancashire in northwest England, and all four who are between the ages of 21 and 31 are being questioned by police.
Police said the four were arrested on suspicion of "failing to disclose information which might be of assistance in securing the apprehension, prosecution or conviction of a person involved in an act of terrorism."
The arrests come after police charged two brothers last month with attending a terror training camp in Syria and firearms offences.