ABIDJAN, Cote d'Ivoire - Cote d'Ivoire's President Alassane Ouattara took the oath of office Friday, five months after the election that nearly ripped this African nation in two and left hundreds dead when the country's strongman refused to concede defeat.

Cote d'Ivoire's President Alassane Ouattara takes the oath of office at the presidential palace in Abidjan May 6, 2011.  [Photo/Agencies]

Ouattara spent much of that time barricaded inside a hotel, surrounded by troops loyal to Laurent Gbagbo, who used the army to terrorize the population. Gbagbo was removed militarily last month and is now under house arrest in a remote town 420 miles (700 kilometers) north of Abidjan.

The price of installing the country's democratically elected leader was steep. Hundreds of civilians were killed, first by the army controlled by Gbagbo and later by the former rebel group that seized control of the country and toppled Gbagbo.

Hours before the ceremony, the United Nations human rights office in Geneva announced that their investigators were headed to a soccer field in an Abidjan neighborhood believed to be the site of a new mass grave.

Inside the presidential palace, Ouattara stood a story above the basement where reporters found more than 500 boxes of rockets in the days after Gbagbo's capture.

Ouattara raised his right hand and swore to protect the constitution in front of Paul Yao N'Dre, one of Gbagbo's closest allies who months earlier had used his position on the country's highest court to overturn Ouattara's victory.

"In front of the sovereign people of Ivory Coast, I solemnly swear on my honor to respect and faithfully defend the constitution," Ouattara said. "And protect the rights and liberties of our citizens."

Callimachi contributed to this report from Dakar, Senegal.