Iraq's government has warned Sweden that ISIS may be planning a terror attack on that country's capital of Stockholm.

The official, who spoke on condition of anonymity to NBC News, said Iraq found intelligence "about an ISIS plan to target the Swedish capital Stockholm," involving seven or eight Iraqi citizens who were former members of al-Qaeda in Iraq.

"Those ISIS militants are Iraqis, and were able to arrive to Sweden in 2015 with those thousands who emigrate from different countries to Europe," the official said.

The U.S. Embassy in Stockholm said Tuesday it "has confirmed that Swedish Police are actively investigating a potential terror threat against Sweden."

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