Seven people have been arrested on suspicion of aiding terrorists by raising money for their cause.
Six men and one woman were arrested under the Terrorism Act 2000 in raids on four properties in London, Cardiff and Coventry.
A 49-year-old man and a 45-year-old woman were arrested in Croydon, south London, two men, 30 and 47, were arrested in Brent, northwest London, two men, 45 and 42, were arrested in Coventry and a 45-year-old man was taken into custody in Cardiff.
All have been taken to a police station in central London where they remain in custody.
The Metropolitan Police said the arrests were part of a pre-planned, intelligence-led operation into suspected fundraising for terrorism overseas.
Another eight search warrants were executed at seven addresses in London, Worthing and Coventry as well as a business premises in Coventry but no arrests were made.