The charges against him specifically point to a campaign of killings and mass rapes of civilians allegedly carried out by his forces.
Members of Bemba's Mouvement de liberation du Congo (MLC), who also fought in the DRC's 1998-2003 war, intervened in Central African Republic in support of then leader Ange Felix Patasse.
The Central African Republic president was battling opposition forces led by Francois Bozize, who subsequently toppled Patasse in a 2003 coup and is the current head of state.
Both Bemba, who had been in exile in Portugal, and Patasse, who lives in exile in Togo, deny the war-crimes accusations.
There was no immediate reaction to Bemba's arrest in Brussels from the DRC government, which has recalled its ambassador from Belgium in a growing diplomatic dispute with its small former colonial ruler.
Relations between the two countries have been strained since Karel De Gucht, the Belgian foreign minister, criticised Kabila's government last month over human rights, corruption and its dealings with China.
Bemba is the first person arrested under an ICC investigation in the Central African Republic, which was opened by Luis Moreno-Ocampo, the court's chief prosecutor, in May 2007.
The ICC, which is based in The Hague and started work in 2002 as the world's first permanent war crimes court, is also pursuing war crimes prosecutions against suspects in the DRC, Uganda and in Sudan, relating to its war-torn western Darfur region.
|The ICC says the scars of abuse will be hard|
to erase but justice is possible [EPA]
Moreno-Ocampo said the ICC is continuing its inquiries into what it says was a widespread and systematic attack against the Central African Republic's civilian population by Bemba's MLC members "during which rape, torture, outrages upon personal dignity and pillaging were committed".
He thanked Belgium for executing the ICC arrest warrant against Bemba.
Moreno-Ocampo visited the Central African Republic in February to hear testimony from victims of the sexual violence which accompanied the fighting in the capital Bangui in 2002-2003 between government troops and opposition fighters.
Rapes outnumbered other crimes, with young girls and old women being gang-raped in public places, the ICC said.
Warning to all
Moreno-Ocampo said Bemba's arrest is a warning to all those who commit, encourage or tolerate sexual crimes.
"There are no excuses for hundreds of rapes. There are no excuses for the rape of a little girl, with her parents watching," he said.
"There are no excuses for commanders ordering, authorising or acquiescing to the commission of rapes and looting by their forces.
"We have evidence that Mr Bemba committed crimes.
"I went to CAR, I met the victims, those who survived the violence, those who survived Aids. We cannot erase the scars.
"But we can give them justice ... The victims will tell their stories in court."