Tension is rising in opposition-controlled areas of Syria between members of the Free Syrian Army (FSA) and Syrian civilians on one side, and fighters from extremist groups, such as the "Islamic State of Iraq and the Levant" (ISIL) and Jabhat al-Nusra (JAN), on the other.
"Transgressions" committed by the two al-Qaeda-affiliated groups and their attempts to impose their beliefs on the population have been met with criticism and resistance by local residents, according to observers monitoring the situation in Syria.
In June, men from the ISIL's "sharia committee" killed a 15-year-old boy in front of his family in Aleppo. His body bore marks of "torture and beating", according to the Syrian Observatory for Human Rights. On July 10th, a civilian in Hasakeh province was tortured to death by JAN fighters.
On July 5th, ISIL fighters shot at demonstrators protesting their presence and behaviour in al-Dana, Idlib province, killing dozens.
And on July 11th, an ISIL member killed Kamal Hamami, a member of the FSA's Supreme Military Council, in Latakia province. Earlier the same month, an Idlib-based opposition chief was beheaded by the ISIL.
"The protest movement by Syrian civilians and members of the Free Syrian Army have noticeably been on the rise of late due to the unacceptable transgressions committed by members" of JAN and ISIL, Observatory director Rami Abdel Rahman told Al-Shorfa.
"These transgressions are in the form of physical eliminations, detention and torture under detention for anyone that shares a different opinion," he said.
Activists and journalists trying to report on these transgressions also have been detained, he added, as was the case in al-Dana in Rif Idlib and in al-Raqa.
These groups "are also constantly trying to take by force all strategic outposts", he said.
In al-Raqa alone, close to 1,500 people have been detained, and eyewitnesses say this number includes children and elderly people held "for trivial reasons", Abdel Rahman said, adding that JAN members who refused to join the ISIL also are among those detained.
Most ISIL members are foreign fighters, he said, and many were proclaimed "emirs" of areas the group declared "Islamic emirates".
Abdel Rahman warned of a potential rise in clashes in upcoming weeks, with Syrian citizens and the FSA on one side and radical groups on the other, especially in Aleppo, Idlib, Rif Idlib and al-Raqa.
These could be triggered by extremist groups insisting on implementing their laws by force and demanding that armed groups not under their command lay down their weapons, he said.
Strategy analyst Yahya Mohammed Ali, a former military officer in the Egyptian army who specialises in terrorist groups, said al-Qaeda's branches in Syria are competing for control over opposition-held areas in a bid to create an "Islamic state" in them.
"The disputes between al-Qaeda's different branches will lead to fierce battles because it is a battle for survival of the fittest," he said. "But these differences might now be put aside in order to quell the rising protests against it."
The escalation of attacks between the FSA and ISIL and the fall of several FSA soldiers such as leader Kamal Hamami put the opposition in an unenviable position, he said.
"The FSA now needs more than ever to eliminate these terrorist elements that are attacking its leaders and soldiers," Ali said. "Not addressing this issue will only lead to an expansion of these extremist groups."
Such an expansion would not only be dangerous for Syria but for all the countries in the region, he said.
Alaeddine Mahmoud, a former Syrian JAN member using an assumed name out of fear for his safety, told Al-Shorfa JAN recruited him in al-Raqa using false pretences.
At the start of his time with JAN, he was subjected to "brainwashing", Mahmoud said.
He said he was told that Islamist groups were acting in accordance with sharia and that their first and last goal was to get rid of the Assad regime.
"After joining JAN, however, I saw nothing except obvious attempts to create an Islamic state," he said.
Mahmoud said he was part of the group for 10 months. Because of his music and Internet skills, he was initially asked to write Islamic songs and post them to websites and social media forums.
His role was later confined to the surveillance and patrol of opposition-held areas, in addition to special missions assigned by "Sharia committees", he said.
During this time, Mahmoud said he got to know a number of the group's members, particularly men from Tunisia and Uzbekistan.
He described the foreign recruits as "not cultured at all". He said their religious knowledge was minimal and that "there also is widespread use of drugs".
Mahmoud said he left JAN because he found himself "in a strange environment that is alien to me and to Syrian society in general". He said the leadership's focus was not on the war against the regime but on sectarian conflict – against the Shia and the region's Christian population.
Extremist groups such as JAN "were at war with anyone who was opposed to Islamist rule including secularists, liberals and FSA soldiers", he added.