Photographs of the bloodied face of a 14-year-old boy executed in front of his parents by jihadists in northern Syria show the extreme justice meted out in rebel-held areas.
Fighters of al-Qaeda front group the Islamic State of Iraq and Syria accused Mohammad Qattaa of blasphemy but a human rights group said he had done nothing more than use a common Arabic phrase that makes reference to the name of the Prophet Muhammad.
Pictures of Qattaa's face, bloodied by the three shots that cut short his life on Monday, spread like wildfire on social media websites, prompting a strong condemnation of his killing from the mainstream opposition.
"If someone shot a dog in the street, people would act," cried the boy's mother, Umm Mohammed, in amateur video footage distributed by activists.
"Where are his rights? He was a child! How could they kill him? They killed him right in front of my eyes ... May God take revenge on them ... I saw his blood streaming down," she wailed.
"We are with neither side [in Syria's raging conflict]. We just look after ourselves ... Why did you kill my son? Is he a terrorist?"
The Syrian Observatory for Human Rights said the militants responsible for the execution were foreign volunteers with the al-Qaeda-linked Islamic State of Iraq and Syria.
Large swathes of northern Syria have fallen into the hands of various rebel groups, some of them Islamist, which have set up their own justice systems in areas they control.
Nadim Houry of Human Rights Watch said: "Executions are on the increase, and a rising number of groups are taking the law into their own hands."
Meanwhile, a key defeat for the rebels and a major split in the ranks of al-Qaeda-aligned jihadists are behind accelerated moves in the United States to arm Syria's opposition, Washington officials have indicated.
John Kerry, the US Secretary of State, postponed a visit to Israel and the Palestinian territories to hold talks with President Barack Obama on the next steps in the Syria crisis.
Officials told US news outlets the Administration was considering not only arming the rebels directly but even imposing a no-fly zone on the regime of President Bashar al-Assad.
State and Defence Department officials, the CIA and other agencies met yesterday to draw up options for Obama.
- additional reporting AFP