"With just a week to go to a presidential election on 9 August, the Rwandan authorities are openly flouting the rules of the democratic game," the organisation said in a statement.
"Press freedom violations, including the jailing of journalists, the closure of news media and the murder of a newspaper editor a month ago, have intensified in the run-up to the election," it added.
RSF said that Rwanda's Media High Council had published last week a list of 19 radio stations and 22 newspapers deemed to comply with its rules.
Those not on the list, including some radios and newspapers with a wide following, have been asked to apply for permits and are de facto banned until a fresh request is approved, the watchdog said.
"The Media High Council?s measures, coming just a few days before the election, are highly suspect," Reporters Without Borders said.
"The aim is to clamp down on the press and prevent journalists from doing their job as independent and impartial observers of the election process."
A journalist who claimed to have uncovered evidence linking the government to the attempted assassination of a Rwandan general exiled in South Africa was found dead last month, almost decapitated.
The regime denied any involvement.
French foreign ministry deputy spokeswoman Christine Fages said Tuesday that "France is attached to the freedom of expression and the freedom of the press in Rwanda, like everywhere in the world."
Paris "supports the action of all those who defend the right to inform" and "that is the reason why we condemned with the greatest firmness the murder, on June 24, of Jean-Leonard Rugambage, deputy editor of the biweekly Umuvugizi," Fages told a regular press briefing.
France has several times called on Rwandan authorities to provide a pre-electoral context "respectful of fundamental freedoms and the democratic rules."
Rwandan President Paul Kagame's regime has been criticised for restricting media and political freedom ahead of the election, which he is widely expected to win comfortably.