Six men have been jailed for conspiracy to murder the former Belgian deputy prime minister Andre Cools, who was shot dead in 1991.
Richard Taxquet (right) and five others were found guilty
Two of the convicted men were Mr Cools' former aide and chauffeur.
Five years ago, a Tunisian court convicted two men of the murder, but legal arguments delayed the trial of those accused of ordering the killing.
One key suspect, former government minister Alain Van der Biest, killed himself after denying involvement.
Mr Cools, a former Socialist leader, was regarded as a kingmaker in Belgian politics.
The murder outside his girlfriend's home in Liege remained a mystery for several years before an anonymous informer accused Mr Van der Biest and several associates of arranging the killing.
The investigation revealed a series of corruption scandals that led to four ministerial resignations, as well as that of Willy Claes, the Nato secretary-general at the time.
On Wednesday, the jury acquitted Mr Van der Biest's cabinet employees Mauro de Santis and Silvio de Benedictis of involvement.
But jurors found six other men guilty.
Four of those convicted - his former aide, Richard Taxquet, chauffeur Giuseppe di Mauro, and two men tried in their absence, Cosimo Solazzo, Domenico Castellino - were given 20 years in prison.
Iachino Contrino and Carlo Todarello received five-year jail sentences.
Mr Cools' son Marcel said: "I am a bit disappointed by the light sentences, but that was not the most important. They were found guilty."