FREETOWN, Sept 17 (Reuters) - Opposition leader Ernest Bai Koroma was sworn in as Sierra Leone's president on Monday a few hours after being declared the winner of a tense election in the West African state. The 53-year-old former insurance executive turned politician, who was runner-up in a 2002 presidential poll, took the oath of office before the country's Chief Justice at State House in the capital Freetown.
