British police have arrested 12 men in a large-scale counter-terrorism operation.
West Midlands police say they detained five men from Cardiff, four from Stoke in central England and three from London.
A spokesperson says they are all being held on suspicion of the commission, preparation or instigation of an act of terrorism in the United Kingdom.
The suspects, aged between 17 and 28, were detained by unarmed officers at about 5am.
The Metropolitan Police Assistant Commissioner, John Yates, has been reported by the BBC as calling the swoop a "large-scale, pre-planned, intelligence-led" operation involving several forces.
"We are unable to go into detail at this time about the suspected offences," Mr Yates says.
"However, I believe it was necessary at this time to take action in order to ensure public safety."