Judges read out their judgment at the Special Tribunal for Lebanon in a village near The Hague in the Netherlands on Tuesday 18 August.
Judge David Re said that 2.5 tons of explosives were into a Mitsubishi truck, adding that the bombing was "undoubtedly a political act".
In February 2005 former Lebanese Prime Minister Rafik Hariri was killed when a huge truck bomb blew up in Beirut. Hariri, a billionaire construction tycoon, was Prime Minister from 1992 until 1998 and again between 2000 and October 2004.
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