By Mark Hosenball
WASHINGTON (Reuters) - The Justice Department has tapped a veteran prosecutor to probe the flow of foreign fighters, including Americans, who are joining Syria's rebels, U.S. officials said, in a sign of heightened alarm over the threat of radicalized militants returning home.
The FBI also has formed a special team to identify U.S. citizens traveling to Syria to fight with anti-government groups, and is working with both intelligence and law enforcement agencies to investigate such individuals, a spokesman said.
U.S. security agencies have expressed growing anxiety for months about a steady stream of Western militants heading to Syria. Most of the foreigners join up with the most extreme factions trying to oust Syrian President Bashar al-Assad, including Jabhat al-Nusra and the Islamic State of Iraq and the Levant.
U.S. and allied officials say their main fear is that veteran fighters, radicalized by their Syrian experience, will launch terror attacks once they return home. Authorities in Western Europe say they have uncovered plots by fighters returning from Syria.
The Justice Department prosecutor assigned to deal with the issue, Stephen Ponticello, works for the department's national security division.
The head of that division, John Carlin, said on Thursday that Ponticello will coordinate investigations into foreign fighters, provide expertise, and meet with foreign counterparts in Europe and elsewhere who are dealing with the same threat.
"We want to make sure that individuals in the counterterrorism section and the U.S. Attorneys throughout the country are focused on this threat," Carlin said at an event at the Brookings Institution think tank.
In late March, the State Department also picked career diplomat Robert Bradtke to deal with the perceived threat. Bradtke will be the lead U.S. diplomat in "engaging foreign partners to prevent and interdict foreign extremist travel to Syria," a department spokeswoman said.
Paul Bresson, an FBI spokesman, said his agency had set up a team of experts within its Counterterrorism Division to scout out Americans involved or interested in fighting in Syria.
Historically, he said, "travel to locations such as Yemen, Pakistan, Somalia, have been of particular concern due to the terrorist groups operating in those regions."
But now "Syria has emerged as an area of great concern due to the ongoing conflict and extremist activity in the region," he added.
Until recently, U.S. intelligence officials had estimated that around 7,000 foreigners have since 2012 joined about 23,000 anti-government rebels fighting with the most militant anti-Assad groups.
On Wednesday, however, State Department spokeswoman Jen Psaki said the estimate now stands at 9,000 foreign fighters who have traveled to Syria since the war started.
She described U.S. allies in the Middle East and Europe as "gravely concerned" by the threat from their citizens traveling to Syria.
Psaki declined to estimate how many Americans have gone to Syria to fight. U.S. officials say that several dozen U.S. citizens or residents have traveled to Syria to fight with anti-government groups.
Hundreds of others from the United Kingdom, Belgium, Germany, France, Italy, Netherlands, Spain and other countries whose citizens are afforded easy entry to the United States also have fought in Syria, U.S. and European officials say.
U.S. authorities already have indicted a handful of individuals for alleged involvement in the Syrian conflict, often on charges of providing material support to militant groups. At least one U.S. citizen, Michigan native Nicole Mansfield, was killed in Syria last year, reportedly while fighting with anti-Assad forces.
(Additional reporting by Aruna Viswanatha.; Editing by Warren Strobel, Paul Simao and Andre Grenon)