BEIRUT     (AP) 
-- On Syria's front lines, al-Qaida fighters and more mainstream Syrian 
rebels have turned against each other in a power struggle that has 
undermined the effort to topple Syrian President Bashar Assad.
After
 violent clashes and the assassination of two rival commanders, one of 
whom was beheaded, more moderate factions are publicly accusing the 
extremists of trying to seize control of the rebellion.
The
 rivalries - along with the efforts by extremist foreign fighters to 
impose their strict interpretation of Islam in areas they control - are 
chipping away at the movement's popularity in Syria at a time when the 
regime is making significant advances on the ground.
"The
 rebels' focus has shifted from toppling the regime to governing and 
power struggles," said a 29-year-old woman from the contested city of 
Homs. "I feel that the lack of true leadership is and has always been 
their biggest problem." She spoke on condition of anonymity, fearing 
retaliation from the fighters and the regime.
The
 infighting, which exploded into the open in the country's rebel-held 
north in recent days, is contributing to a sense across many parts of 
Syria that the revolution has faltered. It threatens to fracture an 
opposition movement that has been plagued by divisions from the start.
The
 moderates once valued the expertise and resources that their uneasy 
allies brought to the battlefield, but now question whether such 
military assets are worth the trouble - not to mention the added 
difficulty in persuading the West to arm them.
"We
 don't want foreign fighters. We have enough men and we want them out of
 Syria," said Brig. Gen. Salim Idris, head of the Supreme Military 
Council of the Free Syrian Army, an umbrella group for dozens of 
brigades.
In strikingly blunt comments in an 
interview with Al-Arabiya on Monday, Idris, a secular-minded army 
defector who has the backing of foreign powers, accused members of the 
Islamic State of Iraq and the Levant of being regime agents and 
"criminals."
That group, formed in April and 
made up of al-Qaida's branches in Iraq and Syria, has taken on an 
increasingly dominant role in the Syrian civil war. Many of its fighters
 are north Africans, Iraqis, Afghans and Europeans who have flocked to 
Syria to join the overwhelmingly Sunni uprising against Assad.
Gunmen
 from the Islamic State of Iraq and the Levant were behind the killings 
of the two rebel commanders, the highest-profile casualties of the 
growing tensions between jihadi fighters and Western-supported rebels.
Kamal
 Hamami, known as Abu Basir, served in the Supreme Military Council. 
Activists say he was shot late Thursday in a clash that erupted after 
militants tried to remove a checkpoint he set up on the Jabal 
al-Turkoman mountain in the coastal province of Latakia. Two of his men 
were seriously wounded in the shooting.
Also 
last week, members of the extremist group killed Fadi al-Qish, the local
 commander of a group affiliated with the mainstream Free Syrian Army, 
or FSA. The fatal attack took place in the village of Dana in the 
northern province of Idlib near the Turkish border. Activists say the 
militants decapitated al-Qish and another fighter and left their severed
 heads on the ground as a lesson to other rebels who challenge their 
rule in the area.
The executions have enraged FSA commanders, who are demanding that the killers be handed over to stand trial.
Activists
 also say extremists have recently been sweeping into villages 
previously controlled by the FSA, taking over crucial resources such as 
bakeries, oil wells and water pumps to secure people's loyalties. In 
several cases, the militants were said to seize weapons from army bases 
and keep them from other rebels.
But what 
alienates the general population is the brutality. The extremists have 
carried out summary executions, public floggings and mass arrests, 
fueling the backlash against them.
In one 
prominent case in Aleppo last month, al-Qaida-linked militants executed a
 15-year-old boy, Mohammad Qattaa, accusing him of being an "infidel" 
for mentioning Islam's Prophet Muhammad in vain. Gunmen shot the boy 
dead in front of his parents near a stand where he sold coffee in a 
killing that sparked rare local protests against them.
In
 many parts of Aleppo and Idlib and Homs, where a suffocating stalemate 
has been in place since last year, residents say their support and 
patience for the rebels is fraying.
In Aleppo 
last week, residents staged a protest at a checkpoint against a blockade
 imposed by the militants on government-held districts, because the 
blockade created food shortages at the onset of Ramadan, the Muslim holy
 month. The protest led to a physical quarrel between supporters and 
opponents of the siege and ended with gunshots fired in the air to 
disperse protesters.
Syria's uprising started 
in March 2011 as an Arab Spring-inspired revolt against the decades-long
 Assad family rule. It eventually transformed into an insurgency and 
civil war in response to a brutal government crackdown against the 
protests. More than 93,000 have been killed and millions uprooted from 
their homes.
The rebels are a disparate mix of
 ordinary citizens who took up weapons, army defectors, moderates and 
hard-liners, and increasingly, jihadists who have trekked to Syria from 
all over the world. A shortage of weapons and the inability of external 
players to interfere in the conflict to tip the balance in favor of one 
side or another has worked against the rebels.
Some
 FSA commanders are trying to tamp down the dispute with the al-Qaida 
militants, mindful of the damage the infighting has done to their cause.
"Their
 actions are despicable, but we will not be drawn into a fight with 
them," said one commander, who declined to be named so as not to 
aggravate the situation.
FSA spokesman Loay al-Mikdad was less delicate.
"I
 think they should come out in public and tell the Syrian people why 
they are in Syria. Is it to fight Bashar Assad or to impose a specific 
agenda on the Syrian people?" he asked.
"We 
never see them on the battlefield anymore," he said of the al-Qaida 
militants. "We only see them in liberated areas either next to oil wells
 or trying to impose specific agendas on territories."
The
 dispute is not restricted to Islamic militants versus moderates. In the
 north, there has also been deadly infighting between Kurdish and Arab 
groups over control of captured territory along the border with Turkey.
"This
 infighting is very dangerous and is undermining our revolution," said 
Mohammed Kanaan, an activist based in the northern province of Idlib. 
"People are fed up and tired. ... They are starting to hate both sides,"
 he said via Skype.
Rami Abdul-Rahman, 
director of the U.K.-based Syrian Observatory for Human Rights, said the
 al-Qaida militants are working to entrench themselves and secure a 
place in a post-Assad Syria.
"They are trying to control everything, they have a lot of money," most of it from private donations, he said.
Still, al-Mikdad ruled out a scenario similar to the Iraqi one, when U.S.-allied groups of Sunni fighters battled al-Qaida.
"Until
 now, the FSA does not consider itself in confrontation with these 
groups. Our weapons are directly only against Bashar Assad's troops," he
 said in a TV interview.
"But if a fight is imposed on us, we will defend ourselves," he said.
...............
 AP correspondent Yasmine Sakr contributed to this report.