The company inaugurated servers in about half of its new, 300,000-square foot (28,000-square meter) facility outside the city Lulea Wednesday, saying it should improve the social network's performance in Europe.
Facebook director of site operations Tom Furlong told the Associated Press the company will expand capacity at the site gradually to serve a large chunk of Facebook's European users.
Facebook is one of nine major U.S. Internet providers whose customers' usage is swept up every day by an NSA counterterror surveillance program. The secret court order that authorizes the program, named PRISM, only allows it to examine foreigners' internet usage overseas.
Furlong didn't want to comment on the program but said the data stored in Sweden is replicated in other locations in the U.S.
Jon Karlung, a campaigner for Internet freedom and CEO of Swedish Internet service provider Banhof, said the fact that the servers are located in Sweden doesn't change anything.
"Everything is mirrored so there will be no security for those who use it," he said.
When Facebook announced its plans to build the new server farm in Sweden two years ago, Internet activists warned it would expose users to potential eavesdropping from Sweden's National Defense Radio Establishment, also known by its Swedish initials FRA.
Karlung on Wednesday said the NSA program appears to be much more far-reaching than the FRA surveillance scheme that has been ongoing since 2008.
"FRA gets a momentary glimpse of what is happening, but PRISM has access to systems where everything from the past is stored," Karlung told the Associated Press, calling the new facility in Lulea a "giant spying center."
Furlong dismissed those allegations with a simple "No."
Facebook said it chose to locate its servers in Lulea partly because of the cold climate - crucial for maintaining the servers' temperature - and access to renewable energy from nearby hydropower facilities. The move reflects the growing international presence of the California-based site, which counts 1.11 billion users worldwide.