Police spokesmen were unavailable to comment on the letters but one police officer said there may have been as many as 10 or 12.
The foreign ministry said it had received “a letter that contained a white powder which was sent to police for analysis.”
“The preliminary report from police was that the powder was harmless,” foreign ministry spokeswoman Sofia Karlberg told AFP.
Swedish news agency TT said public service television Sveriges Television and the Swedish municipalities and counties office in the capital had also received letters.
The online edition of the Dagens Nyheter newspaper reported that the letters were signed by an unknown group calling itself Democratic Fight for Freedom Now.
Dagens Nyheter quoted police spokeman Ove Hagdahl as saying that the texts were “very hostile to immigrants”.
According to TT, the texts included phrases such as “foreign race elements” and “Swedish right of occupation over Sweden”.