Jean-Pierre Bemba Gombo is seen in a courtroom of the ICC. File picture: Jerry Lampen/Reuters

The Hague - Lawyers for Jean-Pierre Bemba, the Congolese ex-vice president whose war crimes conviction was quashed on appeal last week, requested his immediate release on Tuesday from the International Criminal Court.

Bemba, 55, has been in the International Criminal Court (ICC) detention centre since his arrest in 2008. The Democratic Republic of Congo opposition leader was convicted in 2016 of crimes against humanity and sentenced to 18 years in prison.

But that conviction was overturned on appeal last Friday in a major setback for prosecutors. Appeals judges said they could not pin responsibility on Bemba for the killing and raping of civilians by soldiers under his command.

He was the highest-ranking official among only four people who had successfully been prosecuted at the permanent war crimes court since it was set up in 2002.

Defence attorney Melinda Taylor asked the panel of judges during a hearing on Tuesday for Bemba's "imminent interim release to Belgium where his family resides".

Judge Bertram Schmitt said a decision would be made by Wednesday "at the latest".

Normally suspects are immediately released after an acquittal, but Bemba also faces a separate charge for witness tampering during the trial, which could result in a maximum five-year sentence.

The charge for tampering was brought in November 2013 and prosecutors said that Bemba should remain in custody until a final sentence is issued in that case.

But Taylor argued that Bemba has already spent a decade in jail and that the possible maximum five-year sentence for witness tampering could at most add a few months prison time.

"It is not logical that he would risk becoming a fugitive from justice for those three months," Taylor said. Bemba signed a document accepting any conditions the judges might attach to his release, she said.

Upon release, Bemba is expected to leave the Netherlands for neighbouring Belgium, where his wife and five children live.

If he were to return to Congo at any point, that would give an instant boost to opponents of longtime President Joseph Kabila ahead of a December presidential election, when Kabila's allies have indicated he might disregard term limits and stand a third time.

Bemba, who finished runner-up to Kabila in the 2006 election, has a large and loyal following in western Congo and his presence would ramp up pressure on Kabila.

Despite being behind bars, Bemba came third in a recent opinion poll by the Congo Research Group.