Swiss police are hunting for three masked men clad in black who seized the Spanish consulate in the capital, Bern, on Monday and then fled the scene.
Swiss special forces went in - but the intruders had fled
Consulate employees said two of the intruders spoke French with North African accents. They were armed with a pistol and a knife, police reported.
Police stormed the building but found nobody inside.
Two people trapped inside earlier had managed to flee. A driver hurt during the break-in is now in hospital.
Police said he had tried to resist the intruders and had suffered fairly serious head injuries. But he had raised the alarm after fleeing.
A police statement said the intruders broke into the consulate before 0750 (0650 GMT) and must have fled just after 0800 (0700 GMT).
Police spokesman Guido Balmer told BBC News that the two employees who managed to get out had locked themselves in a room after hearing the confrontation at the entrance.
Police say they believe the incident was "criminal, rather than political in nature".
The intruders had told a consulate employee to open the safe, police said, adding that they had not managed to contact the intruders.
Spanish Foreign Minister Miguel Angel Moratinos said the three hooded intruders were robbers.
Swiss police posted snipers around the building and sealed off the area - Kirchenfeld - with armoured vehicles.