Guinea's President Alpha Conde was sworn in for a third term at a ceremony in Conakry on Tuesday following violent elections whose result the opposition rejected.
The 82-year-old pushed through constitutional changes in March allowing him to run despite a two-term limit.
The move led to opposition candidates boycotting the October 18 vote and caused deadly clashes across Guinea.
Conde's main rival, former prime minister Cellou Dalein Diallo, and other opposition figures alleged irregularities in the official poll results that showed Conde won with 59.5% of the vote.
But the constitutional court president said they had produced no evidence and declared Conde the winner.
In a speech at the ceremony, Conde vowed to defend the constitution.
"I Alpha Conde, president of the republic elected in accordance with the constitution, I swear before the Guinean people and on my honor, to respect and scrupulously enforce the provisions of the constitution of laws and decision of justice, to defend the constitutional institutions, integrity of territory and national independence, in case of perjury, that I endure the laws and the rigors of the law," he said.
There is no way for Conde's opponents to appeal the constitutional court decision, leaving him clear to begin a six-year term.
Conde’s actions have raised fears about a democratic backslide in Guinea.
Similar moves were made in the Ivory Coast after President Alassane Ouattara was declared the winner of an election last month after running for a disputed third term.