Armed men have rammed a van full of gas canisters into a Microsoft office in the Greek capital Athens, setting it alight, but nobody was hurt.
They threatened security guards with guns during the attack on the office in the Athens suburb of Maroussi at around 04:35 (01:45 GMT), police said.
The van was destroyed and the floor of the building badly damaged.
No group said it had carried out the attack. Arson attacks have become more frequent during the economic crisis.
They are usually blamed on left-wing extremists but police said it was too early to draw any conclusions.
Microsoft said it would shut its office for the day.
"Staff were told not to come to work today, and probably also tomorrow," company spokeswoman Lia Komninou told Greek channel Skai TV.
The US corporation is the world's largest personal computer software company.
Police quoted by Reuters news agency said at least two people wielding pistols and a machine gun had kept security guards away during the attack.
The attackers drove the stolen van through the office's entrance, the Greek newspaper Kathimerini reports. According to the newspaper, three men were involved.
An investigation has been launched by Greece's anti-terrorism squad, it said.
The fire brigade estimates the damage to be worth about 60,000 euros (£48,000; $75,000), Reuters adds.
Previous arson attacks targeted official buildings, banks or symbols of state power with small bombs or incendiary devices.
They usually happened at night and rarely caused injuries.