By Steve Holland
WASHINGTON (Reuters) - Some of the 100 Americans who went to Syria and Iraq to join up with radical groups like Islamic State have returned to the United States, U.S. officials said on Monday, amid fears that such foreign fighters could pose a security threat at home.
The officials, who briefed reporters on condition of anonymity ahead of President Barack Obama's trip to the United Nations General Assembly this week, did not provide a specific number of Americans who had returned.
For weeks U.S. officials have estimated that 100 Americans have attempted to join up with extremists in Syria and Iraq, including Islamic State.
Asked for more detail about the 100, one official gave this breakdown: "It includes those who've gone, those who've tried to go, some who've come back and are under active — the FBI is looking at them."
Overall, officials estimated 15,000 people from 80 countries have attempted or have gone to Syria and Iraq to join the fight, including 2,000 Europeans.
"What we're looking at is an unprecedented flow. It's really the scale of the problem," one official said.
A central component of Obama's trip to the United Nations is to seek international support for a strategy to deal with the threat of foreign fighters who have sworn allegiance to Islamic State or other groups and seek to return to their home countries, where they could launch attacks against civilians.
The U.N. Security Council is expected to approve a resolution on Wednesday that demands countries prevent and suppress the recruitment and travel to join extremist groups.
Later in the fall, the White House will stage a summit aimed at developing ways to counter the recruitment of extremists.
The U.S. government has already placed representatives in Los Angeles and Boston to coordinate anti-recruitment efforts in the region and plans to place an official with similar duties in Minneapolis, the officials said.
(Reporting by Steve Holland; Editing by Tom Brown)