Norway's intelligence agency says it has information about a "concrete threat" from people who are linked to radical Islamist fighters in Syria.
The head of the Norwegian security service, Benedict Bjoernland, told reporters Thursday that the agency has "reliable information" from a foreign partner about the possibility of an attack "within days." There was no indication of a specific target.
"We also have information that indicates a terror act will be conducted in Norway soon, probably within the next few days. We have no information on who, how, or what target and in which way a possible attack could be carried out."
Bjoernland said authorities hope making the information public will deter the would-be attackers.
He said the information involves people who have been fighters in Syria. The intelligence agency, known as PST, said last month that about 50 people traveled from Norway to Syria to participate in the fighting. About half of those have since returned to Norway.
Some information for this report comes from AP, AFP and Reuters.