British counter-terror police arrested 12 men early Monday in a “large-scale, pre-planned, intelligence-led” operation, they said, according to CNN. The suspects, aged from 17 to 28, were arrested in London, Cardiff in Wales and Stoke in central England. They are due to be questioned Monday, West Midlands police said. They are all of Pakistani descent, a security source who did not want to be identified told CNN. Britain’s domestic intelligence service, known as MI5, led the operation, the source said.