A French court has acquitted former IMF chief Dominique Strauss-Kahn of procuring prostitutes for sex parties in France, Belgium and the US.

He stood, alongside 13 co-defendants, charged with "aggravated pimping".

Strauss-Kahn has always denied knowing that some of the women who took part in orgies he attended were prostitutes.

The sexual habits of the former French presidential hopeful were at the centre of trial hearings in Lille in February.

The verdict brings to a close four years of legal proceedings against Strauss-Kahn, including charges of attempted rape which were later dropped in 2012.

Passing through the brutalist architecture of Lille's courthouse this morning came the colourful parade of characters whose private behaviour has been pored over by the world's media.

Having been subject to moral judgements for months now, they came to hear the legal ones.

In the courtroom, DSK sat, largely immobile, in a dark suit and tie, hands folded in his lap as the defendants walked one by one to the stand to hear their verdict.

When his time came, he stood stiffly at the stand, looking straight ahead as the charges were read aloud.

The man who had one day hoped to be president of France showed almost no response when his acquittal came.

Entering the courthouse before the verdict, the Belgian brothel owner nicknamed Dodo said the trial "was meant to topple DSK".

If it was, it didn't work. And today Dominique Strauss-Khan walked free.

The chief judge said Strauss-Kahn behaved as a client and had not paid the sex workers he met. He only benefitted from others paying them to be present for group parties, the judge added.

Among the others acquitted was Belgian brothel owner Dominique Alderweireld, also known as Dodo, who was accused of supplying prostitutes for the parties.

During the three weeks of hearings in February, sex workers described his rough behaviour at some of the parties.

But Strauss-Kahn said that he was not on trial for "deviant practices". He told the court he participated in the parties because he needed "recreational sessions" amid one of the world's worst financial crises.

The state prosecutor, Frederic Fevre, had already recommended his acquittal, telling the court that they they were "working with the penal code, not the moral code".

Fevre also said that neither the investigation nor the evidence in court had established that he was guilty.

Earlier, five of the six plaintiffs in the case dropped their accusations against the 66-year-old.

While Strauss-Kahn has admitted to being present at the orgies, he has always maintained that he did not know that some of the women involved were being paid.