Hackers have broken in to the Swiss foreign ministry's computer system in an attempt to steal data, forcing parts of it to be shut down for several days.
The "professional virus attack" allowed outsiders to access the computer system to obtain information, the ministry said, but it gave no details on the nature or extent of the breach.
The "well hidden" software used to carry out the data breach was discovered by government and Microsoft technicians on Thursday last week, according to reports.
"In concrete terms, foreign ministry staff cannot use the internet for the time being but can use the internal network," a spokesman said.
The Swiss Finance Ministry and Interior Ministry also experienced computer problems last week, but no link has been established between the three incidents.