Nigerian President Goodluck Jonathan took the oath of office on Sunday following elections judged as the country\'s fairest to date though marred by deadly post-poll riots. Jonathan, 53, was sworn in amid tight security at a colourful ceremony witnessed by more than two dozen heads of state in the capital of Africa\'s most populous country. In an oath administered by chief justice Aloysius Katsina-Alu, Jonathan sporting a fedora hat swore to be \"faithful and bear true allegiance\" to Nigeria and \"discharge my duties to the best of my abilities.\" Profile: Goodluck Jonathan The 53-year-old southern Christian beat his main opponent, an ex-military ruler from the mainly Muslim north, in the April 16 vote, but three days of rioting following the election killed more than 800 people.