Rwandan president Paul Kagame was been sworn in for a third term after winning the recent election with nearly 99% of the vote.
Many African leaders attended the ceremony in the capital, Kigali.
The long-time president had described the August 4 election as "a formality" while campaigning.
The East African nation has virtually no political opposition, and critics accuse Mr Kagame of being intolerant of dissent. He denies this.
Mr Kagame has been de facto leader or president since the end of the 1994 genocide. Because of a change to the constitution in 2015, he can legally stay in power until 2034.
Human Rights Watch said that in the months leading to the election it documented a pattern of harassment, arrests and detentions of opposition party leaders and supporters, activists and journalists.
Several were forcibly disappeared or prosecuted after making comments critical of the current government or ruling party, the rights group said.
Human Rights Watch's Ida Sawyer said: "Kagame's landslide win came as no surprise in a context in which Rwandans who have dared raise their voices or challenge the status quo have been arrested, forcibly disappeared or killed."
Amnesty International had described a "climate of fear" ahead of the vote.