He says the government in DR Congo has not protected them from the Rwandan Hutu militia which escaped from Rwanda after helping slaughter 800,000 Rwandan Tutsis and moderate Hutus in 1994.
He also says he is fighting to liberate all of DR Congo from a corrupt government.
Talking to Al Jazeera in November, Nkunda defended the actions of the CNDP, saying the group was "looking for a solution" to the country's many problems.
"If you can compare Congo with other countries, there is no life, there is no economy, there is no salary, there is no administration, no justice - so how can we think we are destroying anything?" he said.
Fighting in Rwanda
Born in 1967, with Rwandan roots, Nkunda began his military career in the Tutsi-led Rwandan forces which eventually stopped the country's genocide.
He returned to his homeland, at the time called Zaire, to fight with rebels headed by Laurent-Desire Kabila, who in 1997 overthrew the dictator Mobutu Sese Seko with the help of the Rwandan and Angolan armies.
When the Congo war started in 1998, eventually drawing in six African countries, Nkunda became a senior commander in a Rwandan-backed Congolese rebel group which held a big area in the eastern part of the country.
After a peace deal ended the war in 2003, Nkunda joined Congo's army but quit in 2004 to launch the CNDP.
Nkunda led 4,000 soldiers to rise up and capture the South Kivu capital of Bukavu in 2004. An international arrest warrant was issued against him for alleged war crimes committed while occupying the city, but Congolese officials say this has expired.
Human Rights Watch has accused Nkunda's forces of mass killings, torture, rape, and the recruitment of child soldiers.
During fighting in east Congo last autumn, Human Rights Watch said Nkunda's fighters massacred dozens of civilians in the town of Kiwanja after clashing with the pro-government Mai Mai militia.
The fighting, which drew in Congolese government forces, displaced more than a quarter of a million civilians.
In August, Nkunda's fighters pulled out of a tenuous peace process, effectively ending a fragile ceasefire dating back to a January 2008 peace deal.
Nkunda's men and government troops each accuse the other of provoking clashes.
Monuc, the UN peacekeeping contingent, has blamed Nkunda's troops for instigating most of the recent fighting and has called on militias in the east to abide by the January peace agreement.
Nkunda in turn has accused Monuc of bias.
Following his arrest, Al Jazeera's central Africa correspondent Yvonne Ndege said: "My sense is that Nkunda could spend a very long time in a Congolese prison, maybe even for the rest of his life."