GAROUA (Reuters) -Cameroon opposition candidate Issa Tchiroma declared victory late on Monday in the country's October 12 presidential election, urging President Paul Biya to accept defeat and "honour the truth of the ballot box". Tchiroma, 76, a former government spokesperson and employment minister, broke ranks with Biya earlier this year and mounted a campaign that drew large crowds and endorsements from a coalition of opposition parties and civic groups.