Three men have been arrested in the Worcestershire area following an investigation into "international terrorism overseas".
A Scotland Yard spokesman said the men were arrested on Monday by detectives from the anti-terrorist branch.
The men, aged 39, 42 and 34, were arrested under the Terrorism Act 2000. All three are being held in London.
The location of the suspected terrorist activity and the nationality of the suspects have not been released.
A Scotland Yard spokesman said the men were arrested on suspicion of the commission, preparation or instigation of acts of terrorism.
The investigation is separate from the ongoing inquiries into the events in London during July 2005, the spokesman added.