Kamara in a live broadcast by state media alleged the March 31 run-off poll was marred by "massive ballot stuffing, over-voting" and other electoral irregularities."We are challenging the results," Kamara said."We will be taking appropriate legal steps. We urge all our supporters to stay calm as we purse this legal action," he added in the live broadcast Thursday.Bio, Sierra Leone People's Party candidate was declared winner of the country's presidential run-off election Wednesday.The former junta head of the West African nation in 1996, took 51.81 percent of the vote, defeating Kamara in a tight run -off poll.Bio, a retired brigadier was sworn-in and then took his oath of office, minutes after the declaration of the result by the country's chief justice, Abdulai Cham, the Sierra Leone Telegraph reported.He vowed to be president of all Sierra Leoneans at the short ceremony in the capital, Freetown."I will be president for every Sierra Leonean, whether you voted for me or not,"Bio said.He succeeds President Ernest Bai Koroma, who leaves office after serving two five-year terms. Koroma came to power in 2007 in the shadow of a decade-long civil war that ended in 2002.Vote counting in the run-off was delayed after disagreement over the tallying method.The election went to a second round after neither of the candidates achieved the required 55% of the ballot in the first round.Bio led the first round of elections with 43.3% and Kamara, a former finance minister, followed closely with 42.7%. Sierra Leoneans picked from a pool of 16 candidates in the first round, which was held on March 7.Bio will be faced with the challenge of reducing extreme poverty and rebuilding the West African country for its 7.3 million citizens.The country has endured several devastating events in past years, including mudslides last year which left hundreds dead in the capital, Freetown.This was preceded by an Ebola crisis in 2014 which claimed nearly 4,000 lives.