A French judge has issued international arrest warrants for nine close aides of Rwandan President Paul Kagame.
Mr Kagame has always accused France over the genocide
They are accused of involvement in the 1994 shooting down of a plane carrying Rwanda's former president, a death which sparked genocide.
The judge has accused Mr Kagame of ordering the killing. The president denies involvement and says the allegations are politically motivated.
Over 800,000 people died in the 100-day massacres which followed the killing.
The French allegations have sparked anger in the Rwandan capital, Kigali, where around 25,000 people were reported to have taken part in a government-organised demonstration against France.
The protesters paraded through the streets carry placards reading: "France: stop organising a second genocide" and "France get out of Rwanda".
They filled Rwanda's Amahoro National Stadium for a rally, where they chanted anti-French slogans and burnt the French flag.
Government offices and banks closed so that workers could take part in the protest, Reuters news agency reported.
The French judge, Jean-Louis Bruguiere, is investigating the case because the crew of the plane were French and the families filed a case in France in 1998.
Those the judge wants to arrest include armed forces chief James Kabarebe and army chief-of-staff Charles Kayonga. Under French law, Mr Kagame has immunity as head of state.
ARREST WARRANTS ISSUED
James Kabarebe, military chief-of-staff
Charles Kayonga, army chief-of-staff
Faustin Nyamwasa-Kayumba, ambassador to India
Jackson Nkurunziza, working for presidential guard
Samuel Kanyamera, RPF deputy
Jacob Tumwime, army officer
Franck Nziza, presidential guard officer
Eric Hakizimana, intelligence officer
Rose Kabuye, director general of state protocol
Judge Bruguiere has said that only Mr Kagame's Tutsi-dominated Rwandan Patriotic Front (RPF) forces had missiles capable of downing President Juvenal Habyarimana's plane.
He said the attack was carefully planned by the RPF.
Mr Kagame has denied this and has always accused France of having links to those who carried out the genocide.
The International Criminal Tribunal for Rwanda (ICTR) brushed aside suggestions from Judge Bruguiere that Mr Kagame should stand trial there.
"The prosecutor takes instructions from nobody in the world," said Everard O'Donnell, spokesman for the Arusha-based tribunal.
"The crash did not create the genocide," he said.
Mr Kagame has described suggestions that he was behind the assassination of the former president as scandalous.
Thousands turned out to protest against France
After Habyarimana's plane crashed, Hutu extremists started massacring ethnic Tutsis and Hutu moderates.
The genocide came to an end when Mr Kagame's then rebel RPF seized power 100 days later.
The RPF has always said the Hutu extremists shot down the presidential plane to provide a pretext to carry out the genocide.
"That some judge in France whose name I cannot even pronounce has something to say about Rwanda - trying a president and some government officials - that's rubbish," Mr Kagame said on Wednesday.
And at the rally in Kigali, activists hit out at France.
"The French trained Interahamwe [Hutu militias] everywhere in the country but it did not stop them from losing," Francois Ngarambe, president of genocide survivors' group Ibuka told demonstrators.
He accused France of sheltering genocide suspects. "If they want justice, why don't they start with such people," he said.