A leading opposition challenger to President Paul Biya claimed victory on Monday following Cameroon's presidential polls despite a government warning not to announce unofficial results."I was charged with taking a penalty, I took it and I scored," said Movement for the Rebirth of Cameroon (MRC) candidate Maurice Kamto at a media conference in Yaounde."I have received a clear mandate from the people and I intend to defend it until the end."By law each polling station must submit its results, after verification by the Elecam electoral commission, to the Constitutional Court which is responsible for announcing the final, official tally within 15 days.Ahead of the polls, Kamto formed a coalition with the marginal opposition People's Development Front (FDP) but was still seen as unlikely to threaten Biya's 35-year grip on power as the other six opposition hopefuls stayed away.The main opposition Social Democratic Front contender Joshua Osih did not participate in the eleventh-hour tie-up.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook.