has been charged with atrocities committed in the Central African Republic, would obstruct the investigation or commit another crime.
"The continued detention of Jean-Pierre Bemba Gombo did not appear necessary ... to ensure the appearance of Jean-Pierre Bemba Gombo at trial," the court said in a statement.
But Bemba will remain in his holding cell in The Hague until the court finds a country that will take him and conditions for his release are agreed, it said.
The court invited Belgium, Portugal, France, Germany, Italy and South Africa, states to which Bemba had been asked to be released, to provide "observations" on the issue and "any possible set of conditions restricting liberty to be imposed."
Hearings for this purpose were scheduled for September 7-14.
In Kinshasa, Bemba's Congolese Liberation Movement (MLC) welcomed his release and stated that "even if it is only a provisional one, we want to reiterate our total confidence in justice."
"We're relieved, because since the beginning of this affair, we have always said that the prosecution case has no subtance and is essentially a political affair," MLC secretary-general Francois Muamba told AFP.
Bemba, 46, asked the court in June to free him pending his trial on three charges of war crimes and two counts of crimes against humanity for atrocities allegedly committed in the Central African Republic from October 2002 to March 2003.
His lawyers said that he owned property and bank accounts in Belgium, where his children attended school, and had important "social connections" in France.
The court has decided that he would stand trial in his capacity as military commander for acts of murder, rape and pillaging allegedly committed by members of his Movement for the Liberation of Congo, and not as a co-perpetrator.
The prosecution has appealed that decision, and no trial date has been set.
Following that ruling, his lawyers told the court that Bemba's detention was no longer required since the charge sheet had been "significantly reduced."
"We are no longer faced by a criminal (suspected of having) personally committed atrocities," Aime Kilolo told the court.
Bemba was arrested on an ICC warrant in Brussels in May 2008.
Prosecutors claimed his MLC troops aided the armed forces of then CAR president Ange-Felix Patasse in battling a rebel movement led by former CAR army chief of staff Francois Bozize.
After a years-long civil war in the Democratic Republic of Congo, he became one of four vice presidents in a transitional government ahead of landmark 2006 elections in which he unsuccessfully challenged Joseph Kabila for the presidency.
He then led the opposition, but was forced into exile when government forces tried to disarm his private militia in clashes that killed 300 people in March 2007.