Twelve men were arrested early today in a major national counter-terrorism operation, UK police said today. 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 5:am. It is understood that the plans for the alleged attacks were at an advanced stage. 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. 'Searches are now being conducted at the home addresses, plus the address in Birmingham and another residence in London. 'The suspects will be held at police stations in central London, the North West and the West Midlands.' The police statement said five of the suspects were from Cardiff, four were from Stoke-on-Trent and three were from London, including the 17-year-old. The operation is being led by Metropolitan Police Deputy Assistant Commissioner Stuart Osborne, the Senior National Co-ordinator Terrorist Investigations, and is being coordinated from the West Midlands Counter-Terrorism Unit. It also involves the Metropolitan Police's Counter Terrorism Command, South Wales Police and Staffordshire Police, a spokesman said. Metropolitan Police Assistant Commissioner John Yates, national lead for counter-terrorism policing, said: 'This is a large scale, pre-planned and intelligence-led operation involving several forces. 'The operation is in its early stages so we are unable to go into detail at this time about the suspected offences. 'However, I believe it was necessary at this time to take action in order to ensure public safety.' Police are asking anyone with information that may assist the investigation to call the confidential Anti-Terrorist Hotline.(The Daily Mail)