Bosco Ntaganda, the Congolese rebel leader wanted by the International Criminal Court for a raft of war crimes, is a feared military commander believed to run a vast extortion empire in the mineral-rich east of the country.
According to the Congolese government, Ntaganda, said to be a key leader of the M23 rebel group, crossed into Rwanda on Saturday along with hundreds of other rebels fleeing violence with a rival faction of the mainly Tutsi movement.
Kigali has dismissed the claim.
The man known as "The Terminator" for his love of front-line action is said to be among fighters belonging to an M23 faction led by former political leader Jean-Marie Runiga.
Ntaganda and Runiga's faction had been fighting rivals loyal to the group's military chief Sultani Makenga.
Rwandan-born Ntaganda is an ex-general in the Congolese army but is seen as the main instigator of a mutiny by ex-rebels who had been integrated in the regular forces in 2009 but defected in April last year, forming the M23 movement.
A UN report in November said the M23's "de facto chain of command" includes Ntaganda and culminates with Rwandan Defence Minister James Kabarebe.
It piled further evidence against a man who is wanted by the ICC on a grim list of charges including recruiting child soldiers, sex slavery, murder and pillaging.
The ICC issued arrest warrants against Ntaganda in 2006 over crimes committed in the northeastern Ituri region in 2002-2003.
He was again accused of having recruited under-age fighters in the province of North Kivu in the 2012 rebellion.
Human Rights Watch said in May that Ntaganda had forcibly recruited at least 149 boys and young men into his militia.
-- Ntaganda 'kills people easily' --
In an anecdote showing Ntaganda's willingness to get his hands dirty, one woman from Birambizo in North Kivu told HRW that Ntaganda himself visited her village to recruit.
"He asked us to give our children, our students, to him to fight. He came to our village himself," the woman said.
In the words of a child soldier who testified against Ntaganda in The Hague, he is known as someone who "kills people easily".
Born in 1973 in Rwanda but brought up in the DR Congo, the over six-foot Ntaganda -- who has a penchant for pencil moustaches and leather cowboy-style hats -- has enjoyed a life of fine dining and freedom despite the ICC warrant.
"Ntaganda has boldly walked around the restaurants and tennis courts of Goma flaunting his impunity like a medal of honour while engaging in ruthless human rights abuses," HRW senior Africa researcher Anneke Van Woudenberg Van Woudenberg said.
Ntaganda is known as a keen tennis player, and loves jogging and surfing the Internet, according to his lawyer Antoine Mahamba Kasiwa.
According to UN investigators, Ntaganda has managed to amass considerable wealth by running a large extortion empire in North Kivu, manning rogue checkpoints and taxing the area's many mines.
One report said he once earned $15,000 a week from just one border crossing.
In May, a 25-tonne arms cache was found on Ntaganda's farm in Masisi, North Kivu, that included mortars, rifles and small arms.
Ntaganda had fled Rwanda to eastern DR Congo as an adolescent following attacks on his fellow Tutsis.
In his late teens in 1990 he joined the Rwandan Patriotic Front, which was based in Uganda at the time and put an end to the 1994 genocide, under current President Paul Kagame's leadership.
Since then he has alternated between fighting in the national army and rebellions, including in the five-year long DR Congo war that claimed at least two million lives and ended in 2003.
He was once a military chief for the Patriotic Forces for the Liberation of Congo and later joined Laurent Nkunda's National Congress for the Defence of the People.
After the 2009 deal that integrated Nkunda's people into the army, Kinshasa was unwilling to arrest Ntaganda and hand him over to the ICC.
Ntaganda is accused of several assassinations when he was second-in-command of a government sweep to flush out militias from the eastern region, during his time as a general in the regular army.
The M23 rebellion and other unrest in the the troubled central African country has displaced more than 2.2 million Congolese since the start of 2012, according to the UN refugee agency.
The UN and Kinshasa have alleged that Rwanda has been pulling the M23's strings and even had men on the ground, an accusation denied by Kigali.