Twelve men, including three from London, have been arrested in a major national counter-terrorism operation, West Midlands Police have said.
The men - five from Cardiff, four from Stoke-on-Trent and three from London - were detained on suspicion of the commission, preparation or instigation of an act of terrorism in the UK.
The suspects, aged between 17 and 28, were detained by unarmed officers at approximately 5am.
West Midlands Police said in a statement: "All were arrested at or near their home addresses, with the exception of one suspect from Stoke who was at a domestic property in Birmingham, according to The Press Association.
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," Radio New Zealand reports.
US military analysts are concerned about the appearance of a new Russian sniper rifle known as T-5000