An international arrest warrant for Agathe Habyarimana was issued late last year by Rwandan authorities, who have called on Paris to pursue genocide suspects living in France.

Her detention comes a week after French President Nicolas Sarkozy visited Rwanda where he admitted that Paris had made serious errors of judgment over the genocide and said he wanted all those responsible for the killings to be punished.

Rwandan authorities welcomed Habyarimana's arrest. "At long last the long arm of the law is finally taking its course," said Rwanda's Justice Minister Tharcisse Karugarama, who declined to tie the detention to Sarkozy's visit.

"It could be a coincidence, but whatever it is, it's a good sign, it's good news," he told Reuters.

France and Rwanda broke off diplomatic relations in 2006 after a Paris judge accused Rwanda's current President Paul Kagame and nine aides of shooting down Habyarimana's plane in April 1994, a catalyst for the massacre in which 800,000 ethnic Tutsis and moderate Hutus were killed in less than 100 days at the hands of Hutu death squads.

Agathe left Rwanda three days after her husband died and moved to France, but Rwandan authorities are convinced she played a key role in plotting the slaughter.

The head of Rwanda's genocide fugitive tracking unit said it had asked for Habyarimana's extradition. "Our priority is to have her tried in Rwanda because this is where she committed crimes against the Rwandan people," said Jean Bosco Mutangana.