Jean-Pierre Bemba denies all charges
War crimes judges have begun hearing evidence against a militia commanded by former Democratic Republic of Congo Vice-President Jean-Pierre Bemba.
His Movement for the Liberation of Congo intervened in a power struggle in neighbouring Central African Republic in 2002 and 2003.
The International Criminal Court pre-trial hearings involve claims of murder and rape. Mr Bemba denies all charges.
He says his troops were not under his command once they crossed the border.
His lawyers told judges in the Netherlands there was not enough evidence against Mr Bemba to proceed to trial.
But in an opening statement, deputy prosecutor Fatou Bensouda told the court of graphic testimony from one man who said he had been raped in front of his family, then forced to watch his wife and children abused.
Mr Bemba is the most high-profile of four Congolese warlords facing trial at the ICC.
"Bemba wanted to traumatise and terrorise the civilian population so they would not support the rebels," the prosecutor said.
Son of famous businessman
Former assistant to Mobutu Sese Seko
1998: Helped by Uganda to former MLC rebel group
2003: Becomes vice-president under peace deal
2006: Loses run-off election to President Joseph Kabila but gets most votes in western DR Congo
2007: Flees after clashes in Kinshasa
"He chose rape as his main method... rapes against mothers in the presence of their children and rapes of children as their parents were forced to watch."
Mr Bemba, 46, was arrested in Belgium last May and extradited to The Hague in July.
Judges have scheduled four days of hearings, then they have 60 days to decide whether to commit Mr Bemba to trial, seek more evidence or free him.
He denies three counts of crimes against humanity and five counts of war crimes, during a five-month conflict that began in October 2002.
Mr Bemba's defence lawyer Karim Khan said the troops had been sent to shore up the legitimate president of the CAR, Ange-Felix Patasse, who therefore bore responsibility for their actions.
Another defence lawyer, Nkwebe Liriss, said that many Africans believed the charges were politically motivated, to remove Mr Bemba from future elections in DR Congo.
He lost a landmark run-off election against President Joseph Kabila in 2006.
He fled the country after being charged with treason after his bodyguards clashed with the army in 2007.
Mr Bemba, a former rebel leader, became DR Congo's vice-president in 2003 under a power-sharing deal intended to end years of conflict.