According to the Aftonbladet newspaper, Borg entered the garage unaccompanied by body guards to meet a car he had ordered from the government's motor pool to take him to a meeting.
Upon entering the garage, which is connected to a loading dock and thus accessible to the general public, an unknown man on his way to deliver a package rushed up to Borg and began shouting at him.
“The man was directed to the receiving dock in one of the garages at the government offices. At the same time finance minister Anders Borg passed by the same spot,” said Säpo spokesperson Patrik Peter to the TT news agency.
“At that point the man began yelling at the finance minister, but there was no physical altercation.”
A Säpo driver, who was not formally employed as a bodyguard but is considered part of the agency's personal protection force, also intervened in order to keep the man away from Borg.
The Swedish Security Service (Säpo), which supplies body guards to government ministers, is reviewing the incident, which took place several days ago.
“We've assessed the incident and changed our routines. What happened won't happen again,” Peter told Aftonbladet.
Commenting on Wednesday to the TT news agency after reports of the incident emerged in the Swedish media, Borg attempted to downplay the confrontation saying he thought the man simply wanted to “say what he thought about the work we are doing”.
When asked about whether or not he thought the matter revealed any gaps in security procedures, Borg said it was up to Säpo to comment on their working methods.
“We live in an open democracy where citizens should be able to get close to their politicians; I think that has enormous value, so I don't think that we should make this into a big deal,” he told TT.
Nevertheless, the government offices have revised procedures so that letters and packages are no longer handed over in the building's garage.
“It was a serious incident and procedures have probably not been the best, so we think it's a valid assessment,” said Peter.
The man who approached Borg has not been charged with any crime.