The embassy did not specify the nature of the threat but referred to last week's suicide bombing in central Stockholm in a statement, the Swedish news agency TT reported Tuesday.
"In response to a threat against the U.S. Embassy, Stockholm, please be advised that the embassy has enhanced its security posture," the statement on the embassy's home page said. "In light of last week's suicide bombing and the increased threat level in Sweden, we think it prudent and necessary to take these additional precautions."
However, an embassy spokesman said the threat is concrete and the measures are not simply a general response to the bombing.
"We have received information that there is a threat against the embassy so we have raised the security level, I can't saying anything more than that," Chris Dunnet said.
Despite the heightened security, consular services would be available as normal and there would be no change to regular business hours, the embassy said in its statement.