The 35-year-old daughter of a tycoon who once bankrolled the ruling Rwandan Patriotic Front said Wednesday she plans to run as an independent candidate against President Paul Kagame in August's elections.
"Everybody is scared to express themselves because they are too scared of the ruling party," said Diane Rwigara, pledging to tackle poverty, injustice and security problems.
Rwigara distanced herself from the FPR after the death of her father, Assinapol Rwigara, in 2015. She says his death was an assassination, but police reject her allegations and say the cause was a road accident.
An influential industrialist, her father made his fortune in real estate and played an important role financing the FPR in the 1990s.
"I am not here to talk about my father," said Rwigara in a press conference in Kigali, admitting however that his death was "one reason" that had prompted her to run.
"We all know here... people... disappeared or... killed," she said, citing reports from human rights organisations.
In 2014, Human Rights Watch said there was a wave of disappearances in Rwanda, in a report that was rejected by authorities.
Contacted Wednesday by AFP, the FPR and Rwandan police declined to comment on her accusations.
"The only people who are given a voice are the people praising the regime," she added.
Rwigara is the fourth candidate to enter the race, joining independent Philippe Mpayimana, Democratic Green party head Frank Habineza and the incumbent Kagame.
A constitutional amendment passed last year means Kagame is able to stand for another seven-year term.
Rwanda is regularly praised for its stability and economic performance but criticised for a lack of political freedoms.