The German authorities have arrested leaders of a militia which operates in the Democratic Republic of Congo - but how strong is the case against them? The BBC's East Africa Correspondent Peter Greste investigates.
Over the past few months, I have been investigating connections between war crimes allegedly committed by the FDLR in the Congo, and their leaders living in Europe.
One of them is Callixte Mbarushimana, an unlikely-looking warlord, elegantly dressed in a suit, tie and overcoat. With his neatly trimmed goatee and easy smile, he looks more like a university professor than the second-most powerful man in one of Africa's most feared militias.
Mr Mbarushimana is the executive secretary of the FDLR - one of the most potent rebel forces fighting in the dense forests and bush-land along the eastern frontier of the Democratic Republic of Congo.
They are, he says, "a military-political organisation to protect Rwandan refugees and to liberate the Rwandan people from the yoke of the fascist regime of the RPF (Rwandan Patriotic Front)".
These are claims that gall human rights workers, the United Nations and countless Congolese civilians, who accuse the FDLR of a catalogue of abuses, including mass rape, murder, forced recruitments, child soldiers, using slaves to illegally exploit minerals.
"It's just a conglomeration of criminals," according to the head of the UN's programme to demobilise the region's armed groups, Greg Alex. "What have they done in the Congo that's been righteous?"
According to UN investigators, FDLR executives operate relatively freely in North America, and Europe. Those connections have infuriated peacekeeping officials in the Congo who have repeatedly called on host governments to dismantle the support structure that keeps the rebels fighting.
"The linkages are clear," said a frustrated Hiroute Guebre Sellassie, head of the UN's peacekeeping force in the province of North Kivu.
"The FDLR has remained cohesive as it is now because of the political leadership in Europe. These are people that encourage those in the field to kill, to rape every day. These are crimes, so they should be prosecuted."
The FDLR's president, Ignace Murwanashyaka, lives in Mannheim in Germany. He was arrested on Tuesday, charged with being a leader of a terrorist organisation, of war crimes and crimes against humanity.
In interview after interview, serving and former FDLR officials told me that he is not only the ideological and political force behind the movement, he is its supreme military commander.
He is "like President Obama," according to the FDLR's spokesman in the Congo who goes by the nom de guerre of "La Forge".
"Just as President Obama is also the commander-in-chief of the US armed forces, so President Murwanashyaka is our military leader as well."
The BBC has obtained a log of calls from satellite phones owned by senior FDLR commanders that shows a regular and consistent communication with leaders in the diaspora, notably Ignace Murwanashyaka.
The evidence - supported by testimony from former officers - suggests that he personally directed strategy and approved operations.
Captain Busokoye Donat is a former FDLR officer now in Rwanda under the demobilisation scheme. He used to be in charge of officer training before taking over what he described as "civil defence" - which is training civilian supporters in weapons and military tactics.
"You have to understand that in our organisation, Dr Murwanashyaka is like God," he said.
"He might not give tactical orders - that's the job of the officers who know the situation on the ground - but every operation is run past him for approval."
"He knows everything that happens in the field."
I asked Donat about reports that the FDLR is recruiting child soldiers.
"We have been losing a lot of troops through DDRRR (the UN's demobilisation programme) so we have to go to schools to get more soldiers. We have no choice," he said.
"Does Dr Murwanashyaka know this?" I asked.
"I told you. Dr Murwanashyaka knows everything that happens."
Donat also linked the leader to attacks on innocent villagers.
"I personally saw a telegram in which President Murwanashyaka told commanders that they should attack villages to force civilians to flee."
"That's to put pressure on the international community and Rwanda to negotiate with us," Donat said.
Before his arrest, we asked Mr Murwanashyaka for an interview. He referred us to his executive secretary Callixte Mbarushimana in Paris.
Mr Mbarushimana denied complicity in war crimes. "I am in a country where justice works. I am ready to face justice if there are any allegations that come with evidence."
"I have always claimed my innocence and I am ready - I repeat ready - to face justice if they come with allegations."
Mr Mbarushimana fiercely defended the FDLR's human rights record. "There is no FDLR policy to attack any civilian population," he said. "We condemn all those abuses. We have consistently called for an international investigation so that they can identify the authors of those abuses and bring them to justice. That is our policy."
The French authorities told me Mr Mbarushimana has broken none of their laws. They said free speech legislation protects his right to act as the organisation's spokesman, and they have not received any formal request for an investigation.
Crossing Continents: Congo Connection is broadcast on BBC Radio 4 on Thursday, 19 November 2009 at 1100 GMT and repeated on Monday, at 2030 GMT. It is also broadcast on the World Service's Assignment programme on Thursday, 19 November 2009
You can also listen to Crossing Continents on the BBC iPlayer or subscribe to the podcast .