It said that Ali Saqr al-Qasem, 20, shot his mother, Leena, in the head with an assault rifle in front of a large crowd
An Islamic State jihadist executed his own mother in public after she tried to persuade him to quit, according to new reports.
The Syrian Observatory for Human Rights, which monitors the war in Syria from London, said that a number of reliable local sources told it of the killing, which took place on Wednesday.
Activist group Raqqa is Being Slaughtered Silently (RBSS) also reported the incident.
It said that Ali Saqr al-Qasem, 20, shot his mother, Leena, in the head with an assault rifle in front of a large crowd.
It is believed that Leena, 45, who lived in the town of Tabqa, near the Islamic State of Iraq and the Levant's capital Raqqa, but was originally from the coast, told her son she wanted to leave and wanted him to come with her.
He reported her to the group. "She was executed under the pretext of 'inciting her son to leave the Islamic state and escaping together to the outside of Raqqa, and that the Coalition will kill all members of the organisation,” the Observatory reported.
Her son executed her near the main post office building, where she worked.
Hundreds of people gathered to witness the killing, as is common with such events.
Isil have executed a number of women in recent weeks, including Ruqia Hassan, a "citizen journalist" from Raqqa who reported on life inside the town on her Facebook page. She disappeared in July, and her family were informed of her death on January 2.
At the weekend, the group also posted video online of five Isil "'executioners", led by a man with a British accent, killing five men for passing information to the activist group Raqqa is Being Slaughtered Silently.
The killings may be connected to widespread reports that Isil is suffering a crisis of morale, with many foreign fighters trying to escape and return home.
The Observatory reported on Dec. 29 that Islamic State had executed more than 2,000 Syrian civilians in the 18 months since it declared its "caliphate" over the territory it controls in Syria and Iraq. They included people killed on the grounds of homosexuality, practising magic and apostasy.
Islamic State (Isil)
What is Isil? An Islamic extremist group controlling territory in Syria and Iraq
What is it called? In the West, the group is usually known as Isil (Islamic State of Iraq and the Levant) or Isis (Islamic State of Iraq and Syria). In June, the militants said that wanted to simply be called Islamic State in recognition of the self-declared caliphate
What about 'Daesh'? Daesh is an abreviation Dawlat al-Islamiyah f'al-Iraq wa al-Sham, and is the derogatory name used by many Muslims for Isil. Following the Paris attacks, the French government is now using this term
What are its aims? A worldwide Islamic caliphate - a religious government - without borders
What terror attacks has it carried out? Isil has claimed responsibility for the Paris attacks of 13 November 2015, the explosion of a plane travelling from Egypt to Russia, and the individual killings of Western hostages, including James Foley and Alan Henning
How is the group funded? Looting, extortion and the possession of oilfields providing an estimated £1.8m in revenue per day
How much territory does Isil control? An area of the Middle East that is roughly the size of Belgium
Where is it based? Isil's HQ is understood to be in the city of Raqqa, Syria