LONDON: British police Monday arrested a dozen men suspected of plotting a large-scale terror attack – the biggest anti-terrorist sweep since April 2009, when 12 men were detained over an alleged Al-Qaeda bomb plot in the northern city of Manchester. Police who swooped in on the men's houses early in the morning were unarmed, suggesting any planned attack was not imminent. The men were arrested in London, the Welsh city of Cardiff and the English cities of Birmingham and Stoke-on-Trent. The plot was directed at targets inside the United Kingdom but counterterrorism officials declined to give more details. “The operation is in its early stages so we are unable to go into detail at this time,” said John Yates, Britain's senior counterterrorism police officer. Officers said the men range in age from 17 to 28. Police have up to 28 days to question them before they must be charged or released. A British security official said the arrests were not thought to be part of any planned holiday season attack. Iraqi officials had claimed last week that captured insurgents believed a recent suicide bombing in Stockholm was part of a series of planned attacks during the Christmas season. Those claims were rejected by both British and German officials, who insisted there are no specific threats to their countries over the festive period. In October, the US State Department advised American citizens living or traveling in Europe to be wary amid reports that terrorists were planning attacks on a European city.