Ekathimerini reported three armed men driving a stolen truck threatened security guards at the building's entrance with pistols, then forced their way inside. According to
Athens News the truck was laden with homemade explosives which the armed men detonated.
The truck was burned in the fire which caused heavy damage to the ground and first floors of the Microsoft building. Police found gas canisters and containers of flammable liquid.
Ta Nea reported the attackers fled the scene.
More than 100 people work at Microsoft's office at 221 Kifisias Avenue in Marousi. Staff have been told not to come into work.
Police have estimated the damage at 60,000 euros. No one was injured in the attack.
