Jean-Pierre Bemba, who was provisionally freed Tuesday by the International Criminal Court following an acquittal last week, is a former warlord and adversary of Congolese President Joseph Kabila.
His interim release relates to a case in which he was handed a one-year jail sentence and fined 300,000 euros ($350,000) in 2017 for bribing witnesses during his main war crimes trial.
He is still awaiting sentencing on July 4 in a secondary trial which he lost on appeal.
Bemba, a former vice president of the Democratic Republic of Congo however won his main war crimes trial on appeal in which he was previously convicted and sentenced to 18 years for rapes, killings and looting committed by his militia in the Central African Republic (CAR).
Appeal judges said the 2016 verdict had "ignored significant testimonial evidence" that Bemba had had only limited ability to intervene.
The 55-year-old started life in Bogada in the northwest Equateur province of what is now the DRC, the son of a rich businessman close to dictator Mobutu Sese Seko, who ruled from 1965 until his ousting in 1997 and had named the country Zaire.
Young Bemba was schooled in Belgium, DRC's former colonial master, and went on to take over family businesses, using his popularity in the capital Kinshasa to build his wealth and expand into sectors such as mobile phones, air freight and television.
A former business associate described the heavy-set, round-headed Bemba — an imposing 1.90 metres (6 feet, 3 inches) tall — as "too impulsive, too authoritarian" as a boss.
"The social side was not his strong suit," the source added.
Bemba left Kinshasa in 1997 when the late rebel leader Laurent Desire Kabila, father of current president, overthrew Mobutu and gave the country its current name.
A 1998-2003 war drew foreign armies on rival sides into the vast central African nation with fabulous mineral wealth.
Bemba became leader of the Congolese Liberation Movement (MLC) rebels, a 1,500-strong force backed by neighbouring Uganda and opposed to the Kabila regime.
Bemba has spoken with pride of his years in the bush, where his men controlled Equateur province and the border region with the Central African Republic.
Bemba sent his fighters into the neighbouring CAR in October 2002 to help put down an attempted coup against then president Ange-Felix Patasse, sparking a months-long campaign of horrific abuses by MLC troops against the civilian population — the basis of the charges that would be laid against him in The Hague.
After the Congolese war ended in 2003, Bemba laid down his arms and was awarded one of four vice-presidential posts shared among wartime rivals in a transitional government.
In 2006, he lost a presidential run-off against Joseph Kabila, who had been rushed to power by politicians after the 2001 assassination of his father.
After the poll defeat, Bemba vowed to lead the opposition and was elected to the national Senate.
However, he refused to let his militia be integrated into the ranks of the regular army, insisting he needed the MLC to ensure his own safety.
In March 2007, an armed stand-off erupted into violence in Kinshasa, claiming at least 300 lives, according to the United Nations.
As the government brought charges and the courts began to move against Bemba, he quit the country, ostensibly to seek medical treatment in Portugal.
He left Kinshasa escorted by UN armoured vehicles on April 11, 2007. Until his arrest in Brussels in May 2008 on an ICC warrant, Bemba lived between Portugal and Belgium in what he called "forced exile", insisting he would yet return home to take up an opposition role.