'Credible' Terror Threat in Norway, US Officials Say Norwegian intelligence says it was warned of imminent, "concrete" threat.

 -- There is a “credible” threat of a terror attack in Norway in coming days, U.S. officials said following a stark warning from a top Norwegian intelligence official.

Earlier today Benedicte Bjoernland, the head of the Norwegian security service PST, said the country had received “reliable information” about an imminent, “concrete threat” to Norway from extremists who fought in Syria, according to a report by The Associated Press. Bjoernland feared the attack would take place “within days.”

“It was unspecific about what the target might be,” Bjoernland said.

U.S. officials told ABC News the threat to Norway was “credible,” but declined to provide details.

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The AP reported the PST estimated some 50 people have traveled from Norway to fight in the civil war in Syria, about half of whom have returned home.

Top U.S. security officials have been warning for months about the threat to the American homeland from U.S. or Western passport holders who traveled to Syria to fight. Last month a person briefed on intelligence on U.S. fighters in Syria said about 100 Americans had gone over to pick up arms in the Middle East conflict.

In January ABC News reported “dozens” of people were already under surveillance within the U.S. after having returned from Syria.

Last week the U.S. State Department designated a Norwegian alleged member of al Qaeda’s Yemen affiliate as a terrorist, but a U.S. official said he was not likely linked to the current threat.

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