Significant numbers of American and European jihadists are traveling to Syria to join Islamist rebels, prompting new fears of a future wave of al Qaeda terror attacks in the United States and Europe, according to U.S. officials.
Several thousand foreign terrorists, as well as Americans, are joining the Islamist faction of the now-divided Syrian rebels battling the regime of Syrian President Bashar al-Assad.
Most are joining the al-Nusra Front, al Qaeda’s main terrorist group in Syria, along with smaller Islamist militias made up of nationals from more than a dozen foreign countries.
A U.S. official familiar with intelligence reports said the influx of Americans and Europeans to Islamist rebel forces in Syria is increasing the threat of future terrorists attacks here and in Europe.
"There’s a real concern in the U.S. government about what happens to these guys when they are done and they come home," this official said. "Right now they are getting training to be al Qaeda terrorists."
Said a second official: "The Syrian opposition is benefiting from a steady flow of foreign fighters who seem to be joining a variety of Islamist-oriented brigades or starting up nationality-based units."
The second official said a few hundred Europeans currently are in Syria and are mainly Sunni Muslims who traveled over land to reach the rebel groups. "Of course there’s concern that trained-up in Syria they could eventually reverse course and threaten their home countries," this official said.
U.S. intelligence agencies have been closely monitoring the flow of foreign terrorists into Syria for the past year. They have watched scores of jihadists joining mainly the al-Nusra Front each month. Others have joined the Chechen-led Jaysh Al Muhajirin wal Ansar, which has fought together with al-Nusra.
Al-Nusra also joined forces with the Iraqi al Qaeda group, Islamic State of Iraq, to create a new group called the Islamic State of Iraq and the Levant.
U.S. intelligence estimates put the number of foreign fighters in Syria at up to 6,000 people, of which around 17 percent are thought to be from outside the region.
Most of the foreign fighters are from Middle Eastern, North African, and Central Asian states, including Libya, Egypt, Jordon, Kuwait, Lebanon, Morocco, Tunisia, Saudi Arabia, Qatar, Algeria, and United Arab Emirates.
However, the terrorists that are entering Syria from the West are raising new concerns about future domestic terror attacks. Included in this group are jihadists from the United States, Russia, Chechnya, Canada, France, Ireland, Kosovo, and Britain.
For many, the fighting is the first experience of putting their radical Islamic faith into action on the battlefield, the officials said.
Germany’s Interior Minister Hans-Peter Friedrich was quoted in the online Neue Oz Online in May as saying there were as many as 700 European jihadists in Syria.
A spokesman for the National Counterterrorism Center had no immediate comment on the number of American jihadists estimated to be fighting in Syria.
Matthew G. Olsen, director of the National Counterterrorism Center, said during a speech to the Aspen Security Forum last month that his centers major concern is the flow of foreign fighters to Syria.
"Syria has become really the predominant jihadist battlefield in the world," Olsen said. "We see foreign fighters going from western Europe and, in some cases, in a small number of cases from the United States to Syria to fight as part of the opposition."
Olsen said the security concern is that the fighters will become further radicalized and train end "then returning as part of really a global jihadist movement to western Europe and potentially to the United States."
According to the officials, most of the western jihadists are either Muslim immigrants or converts.
It is these Caucasian converts that are raising security concerns, the officials said. Al Qaeda has been trying for years to recruit Americans and Europeans as terrorists because they are believed to be capable of more easily evading western security monitoring.
Patrick Poole, a private counterterrorism analyst, said terrorist groups have welcomed Americans joining their ranks.
"Their presence serves as a vehicle for recruitment and fundraising from the West, which is what we saw in recent years with al-Shabaab recruiting and fundraising from the Somali communities in the United States," Poole said in an interview.
"These American jihadis are used for propaganda purposes, extending the group's message into the heart of infidel lands, as we've seen in the cases of Omar Hammami, and just last week, al Qaeda's chief English-language spokesman Adam Gadahn."
Gadahn, an American, said in a statement in July that Syria is the next target for takeover by al Qaeda, and he urged jihadists in Syria not to cooperate with western-backed rebels there.
On Sunday, Gadahn issued another statement calling for terrorist attacks on western diplomats in the Arab world.
Poole said Syria today is similar to the 1980s jihad in Afghanistan against the Soviet occupation, which was a focal point for building terrorist networks in the United States for domestic attacks.
"Undoubtedly, the examples of Americans joining up with Syrian jihadists will play a role in continuing the radicalization of future home-grown terrorists," Poole said. "Islamic groups here will hold up the example of Amiir Farouk Ibrahim, the Egyptian-American who was killed in Syria just a few weeks ago and who was radicalized at a community college right here in my hometown of Columbus, Ohio."
Another example was Nicole Mansfield, a single mother from Flint, Mich., who was killed traveling with al Qaeda fighters in Syria last May.
Both will be used as examples for American Muslims to follow, Poole said.
Outgoing Deputy CIA Director Michael Morell said the threat of terrorism emanating from Syria is now the top priority threat for the agency.
"It's probably the most important issue in the world today because of where it is currently heading," Morrell told the Wall Street Journal in an interview published Aug. 6.
Iran, the global threat of al Qaeda, and North Korea are other major threats, according to Morrell.
Morrell said more foreign fighters are fighting with al Qaeda-linked groups in Syria than those who joined terrorists in Iraq at the height of the U.S.-led intervention there.
Syrian government weapons that are being taken by rebels are fueling the violence in Syria, and the fighting could spread to Lebanon, Jordan, and Iraq.
On al Qaeda, Morell said the group has changed and its leadership degraded, and with that change the threat of a large-scale attack on the United States has decreased. However, attacks on U.S. diplomatic posts could take place, he said.
"If we don't keep the pressure on them, they will reconstitute," he said. "I worry about complacency in the face of that."
The Obama administration has agreed to provide covert aid to Syrian rebels but is concerned that the aid may end up being used by terrorists.
The Free Syrian Army, made up mainly of Syrian army defectors, is the main group the administration hopes to fund.
However, other countries that are providing aid to the rebels are not discriminating between the Islamist rebels and the more secular Free Syrian Army.
On Saturday, Iraqi Prime Minister Nouri al Maliki warned that weapons and fighters from Syria are also spreading into Iraq.
"The weapons provided to those killers in Syria have been smuggled to Iraq, and those wolves that came from different countries to Syria are now sneaking into Iraq," Maliki was quoted as saying at a youth meeting.
Meanwhile, Germany’s Bild newspaper reported Aug. 19 that al Qaeda is plotting attacks on Europe’s high-speed rail network.