BEIRUT - The involvement of Islamist groups in the takeover of a major military base in Syria's north is the latest example of the increasing role that jihadist organizations are taking in the war to oust President Bashar Assad, say experts.
But as fighting has gone on for months, the main rebel groups that once spurned the jihadists because many were foreigners are now welcoming them, says Thomas Pierret, a researcher from the University of Edinburgh who specializes in Islamic factions.
"Radical Islamists are very visible," Pierret says. "They always fight on the front line because they're seeking martyrdom. For that reason, other groups often ask them to spearhead attacks.
Syria's SANA news agency said a car packed with explosives blew up near a school in a residential part of Qatana on Wednesday. The report quoted medics from a nearby hospital as saying 16 people were killed, including seven children.
No group claimed responsibility for the attack. Similar attacks hit four places in and around Damascus on Wednesday. Three bombs collapsed walls of the Interior Ministry building, killing at least five people. One of the dead was Syrian parliament member Abdullah Qairouz, SANA reported.
The Obama administration has refused to officially back a particular rebel faction in Syria because it said it was not known which were led by moderates and which were influence by Islamic terror groups.
This week the Obama administration designated one such jihadist outfit, Jabhat al-Nusra, as a terrorist group. The move was designed to marginalize the group and lessen the odds that it is seen as a credible player in a post-Assad Syria should the rebels win.
But the reaction of the Free Syrian Army gave the opposite impression.
"Al-Nusra Front has never done anything illegal or worth condemning," Col. Abdel Jabbar al-Okaidi, head of the Free Syrian Army in the battleground province of Aleppo, told Agence France Presse. "They are fighting side by side with us.
"The United States should blacklist as terrorists the leaders of the regime," Okaidi said. "They are massacring civilians, and destroying mosques and houses."
The Free Syrian Army, a rebel volunteer force that includes officers who deserted from the Syrian Army, was at first wary of the foreigners but has come to welcome them to the fight.
Refused direct military assistance from the West, rebel groups that have been fighting Assad since March 2011 now welcome help from groups that are self-avowed anti-American and anti-Israel organizations.
"We might not share the same beliefs than Jabhat al Nusra, but we are fighting the same enemy," said Tamer Muhiedine, a spokesman for the rebel Free Syrian Army in the Aleppo region.
The government of Iraq has said that Jabhat al Nusra is an affiliate of al-Qaeda in Iraq, which carries out terror attacks in Iraq and nearly plunged the country into a civil war after U.S. forces invaded and ousted dictator Saddam Hussein. It calls the United States and Israel enemies of Islam and opposes Muslim sects it considers apostates, such as Syria's Shiite Alawites.
The Syrian army's abandonment of the Sheikh Suleiman military base outside Aleppo followed weeks of fighting in which radical groups took a leading role. Videos released by anti-Assad activists and posted on the Internet showed that the black Islamic flag similar to that used by al-Qaeda has been raised on a pole at the base
The withdrawal of Syrian troops came after the rebel groups claimed last week to have downed a military helicopter leaving the base. Anti-Assad activists posted a video on YouTube showing a helicopter plunging to the ground in a ball of flames while rebel fighters shouted: "God is great."
Pierret said the popularity of jihadist groups is on the rise in Syria because of their perceived courage and discipline.
"However, their military prowess does not necessarily reflect their actual weight on the ground," he said.
The Free Syrian Army said it joined with other jihadist groups, such as Oussoud al-Sunna, to take the base. But AFP reported that jihadist groups acted alone. Muhiedine disagreed.
"The siege of the base was long and tricky due to its location among four rocky hills. We lost about 60 men in the last few days," he said.
Over 100 regime soldiers were taken prisoner, he said, while the rest were either killed, fled or had defected earlier. The FSA said it seized large quantities of weapons, including anti-aircraft batteries, mortars and rockets.
"With the takeover of the regiment post and the Sheikh Suleiman base, the FSA has full control of the region stretching from Aleppo to the Turkish border," Muhiedine said.
Assad has been receiving assistance from Russia and Iran. Russian Deputy Foreign Minister Mikhail Bogdanov offered the first suggestion yet from a top Russian official that Assad's regime may be in trouble.
"We must look at the facts: There is a trend for the government to progressively lose control over an increasing part of the territory," Bogdanov said during hearings at the Kremlin advisory body, the Public Chamber. "The opposition victory can't be excluded."