Those committed to getting justice for the genocide victims want to know how fugitives such as Kabuga find refuge in France -- and why it took so long to track him down.

Kabuga, now 84, faces trial at an international tribunal after his arrest on Saturday.

He is accused of being one of the organisers and financiers of the genocide carried out by ethnic Hutu extremists against Tutsis but also moderate Hutus between April and July 1994, in which at leasIntt 800,000 people were slaughtered.

According to the UN indictment filed against him, Kabuga -- once one of Rwanda's richest men -- used his fortune and business empire to facilitate the killings.

"Kabuga arrested, and arrested in France! It's a thunderbolt, quite extraordinary!" said Alain Gauthier, co-founder of the Collective of Civil Parties for Rwanda (CPCR).

For 23 years, Gauthier and his Franco-Rwandan wife Dafroza -- who lost several members of her family in the genocide -- have been gathering evidence against those they say are responsible.

In 2001, they founded the CPCR to bring before the French courts anyone suspected of having taken part in the genocide and who, they say, often found refuge in France all too easily.

The Gauthiers have given the courts information on some 30 suspects who have taken refuge in France, but only three cases have led to convictions, with the investigations often interminably slow to reach court.

France's dispute role in Rwanda

France's role before, during and after the genocide remains a matter of substantial controversy.

One of the most fiercely disputed issues has been the military aid France gave to the regime of Rwandan president Juvenal Habyarimana, a Hutu, who ruled from 1973 until his April 1994 assassination, which triggered the genocide.

In April last year, President Emmanuel Macron pledged to open the state archives on Rwanda from 1990 to 1994 to a committee of experts in a bid to help track down any suspects living in France. The committee is currently working on its report.

For Rwanda, one such person is Habyarimana's widow, Agathe. She has been accused of being a member of the inner circle of Hutus who planned and carried out the genocide.

For Pierre Nsanzimana, who runs Ibuka France, a support group for survivors of the genocide, Kabuga's arrest is "really massive news".

But that did not, he said, stop them asking questions about what protection Kabuga might have enjoyed -- and how he could have been hiding out in France for so long.

Florent Piton, a researcher at the University of Paris who specialises in Rwanda, has studied just this question.

"I don't know if we can say that France has been a country of asylum, but it has been a sought-after country for genocide suspects, as has Belgium, because of previously existing institutional links," he said.

At the time of the genocide, France took in figures already identified as suspects -- such as Agathe Habyarimana, who left on the first flight out of Kigali a few days after the violence started, he said.

Piton added that the long wait for justice was not necessarily down to political interference, but could be due to lack of resources.

A crimes against humanity unit set up by France in 2012 made a difference in "speeding up investigations," he said, as did smoother relations between Paris and Kigali.

A 17-year-old photo

But Alain Gauthier still has questions.

"How come we have had to wait until 2018 for the prosecutor's office, on its own initiative, to finally arrest a person suspected of having taken part in genocide?," he asked.

"It's not normal that it took 25 years, and that until last year all the files on the judges' desks are the files that we brought them."

One former investigator with France's paramilitary gendarmerie explained why such cases were so difficult.

"We were looking for suspects on the run, who had changed their identity, who were moving around all the time and some of whom had a lot of resources," the investigator told AFP on condition of anonymity.

For Kabuga, who was been wanted since 1997, "we had a 17-year-old photo," he said.

Kabuga's wife lived in Belgium around six years ago, while he had been traced first to the Democratic Republic of Congo and then Kenya, the investigator added.

"Several times we had information putting him in France. We tried to arrest him in Paris one Christmas night, several years ago, but without success."

Francois Graner of the anti-colonial activist group Survie asked: "Why doesn't the criminal justice system take more of an interest in Agathe Kanziga?"

The French administrative system had established that her role in the genocide was sufficiently serious to justify denying her asylum, he argued.

Habyarimana's widow, who lives in a small house in the region of Paris, is "undocumented but not deportable," said her lawyer, who has taken her case to the European Court of Human Rights.

France has never extradited a single person suspected of involvement in the Rwandan genocide.

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