Street riots in France do not appear to be instigated by overseas terrorists, but there are growing fears that Islamic extremists are exploiting the unrest, U.S. officials and private specialists said.
"At this point, it doesn't appear to be foreign-inspired," one U.S. security official said. "But the concern in France is that Islamists might take advantage of it."
The situation is being monitored by France's Central Directorate of General Intelligence, the police intelligence agency, and Directorate for Territorial Surveillance, the counterintelligence and security service.
Many of the rioters are alienated youths, including Muslims, from immigrant families. The CIA estimates that 3 million to 6 million Muslims live in France.
One official said he thinks the riots "don't have a religious cast."
Nevertheless, the attacks have included two firebombings at synagogues in Pierrefitte-sur-Seine and Garges. About 40 rioters confronted police at a synagogue in Stains, the Internet site Jihad Watch reported. French Muslim groups issued a fatwa, or religious edict, on Sunday that condemned the riots.
Steven Emerson, a specialist on Islamic extremism, said Islamists in France are taking steps to exploit the violence.
"What started out as juvenile delinquents engaging in vandalism is being taken over by Islamists," Mr. Emerson said, noting that Jewish targets indicate the Islamist bent of the rioters.
"It has already been taken over internally in France. The question is whether it will be taken over externally," he said.
Mr. Emerson said he does not agree with those who say the violence has nothing to do with Islam.
"It certainly does," he said. "Not Islam the religion per se but the Islamists' separatist culture that is growing in France and other parts of the continent."
Mr. Emerson noted that one figure in France who is pushing for a separate identity for Muslims is Hassan Iquioussen, a cleric who thinks Islamists should be Muslims first and citizens second.
Retired Air Force Lt. Gen. Thomas McInerney, a counterterrorism specialist, said the riots are not the result of poor immigrants opposing the system.
"It is not a directed part of the global extremist network, but it is an offshoot that is well-organized and has similar objectives in intimidating the French government, which they have done," Gen. McInerney said.
The riots will expand unless the French government moves quickly to quell the disturbances, he said.
"It is an assimilation problem that Muslims have, and it will only eventually be resolved through an Islamic reformation," he said.
Harlan K. Ullman, a security adviser to the Center for Strategic and International Studies, said one problem highlighted by the riots is the growing role of fundamentalist Islam - not necessarily extremism - both in Europe and the United States.
"What we're seeing in France is a harbinger of things to come in the future here," Mr. Ullman said. "It could happen here, not in five years but perhaps 10 years."
Fundamentalist Islam is growing rapidly, he said, and its communities are not being assimilated into Western societies.