British police have arrested a Swedish woman at London's Gatwick Airport on suspicion of committing a terror offence. Police said on Friday that the 40-year-old suspect was arrested Thursday afternoon after arriving in Britain on a flight from Italy. The arrest was made by the South East Counter Terrorism police unit. Police say she is suspected of violating the Terrorism Act 2000 by preparing acts of terrorism. She has not been charged or identified and is being questioned by police. Britain has set its official international terrorism threat level at "severe," meaning an attack is judged by intelligence analysts to be highly likely.