Former Congolese vice president Jean-Pierre Bemba has been sentenced to a year in jail and fined him 300,000 euros ($32,000) for bribing witnesses.

Judges at the International Criminal Court handed Bemba the sentence on Wednesday during his trial for war crimes in the Central African Republic.

"The chamber imposes on you an additional 12 months, one year, imprisonment," presiding judge Bertram Schmitt told Bemba, adding a "substantial fine" was necessary "to discourage this kind of behaviour."

Bemba was found guilty in October last year of masterminding a network to bribe and manipulate at least 14 key witnesses, and had "planned, authorised and approved the illicit coaching" of the witnesses to get them to lie at his main trial.

Prosecutors had asked for eight years for Bemba, who is already serving 18 years after he was convicted of war crimes committed in the CAR between 2002 and 2003.

The heavy-set Bemba, 54, wearing a dark suit and light blue shirt, showed no emotion on Wednesday as the additional sentence was imposed by Schmitt in the heavily protected courtroom in The Hague.

The year-long sentence will run consecutively to his 18 years' jail time.

Bemba's lawyer Aime Kilolo received the heaviest sentence among four of the former vice president's associates. He was handed two years and six months for "abuse of trust" as well as "abuse of the lawyer-client privilege".

Bemba's legal case manager Jean-Jacques Mangenda received two years; Narcisse Arido, a defence witness was given 11 months and Congolese lawmaker Fidele Babala was given six months.

All the sentences were well below what the prosecution had requested and none except for Bemba will effectively spend time behind bars, as the judge gave credit for time already spent in the ICC's detention centre.

Once a wealthy businessman-turned-warlord, Bemba became one of four vice presidents in the transitional government of DR Congo's President Joseph Kabila.

In 2006, he lost to Kabila in a presidential election run-off and fled to Europe.

He was arrested in 2008 in Brussels and handed over to the ICC.

His Movement for the Liberation of Congo (MLC), militia has since morphed into a political party and is currently the second-largest opposition group in the National Assembly.