Ibrahim al-Kharit, Syrian writer, and his son Sumar "were shot dead Thursday night by regime forces who raided the neighbourhood of Qasur," Observatory director Rami Abdel Rahman told AFP.
An activist Facebook page, Deir Ezzor News, said they were executed. Kharit was a member of the Arab Writers' Association, and published books including "The Convoy and the Desert" and "The Assassination," it said.
The Syrian regime has repeatedly targeted activists and intellectuals since the March 2011 start of the uprising.
In August 2011, renowned cartoonist Ali Ferzat, whose satirical drawings had been highly critical of the regime, was seized by security forces and pro-regime militiamen and badly beaten, his hands especially.
Independent film producer and activist Orwa Nayrabia went missing in late August after trying to travel to Cairo, and his fate remains unknown.
Activist Adnan Wehbeh was assassinated at his medical clinic in June near Damascus by a security man dressed as a civilian, a watchdog said.
And singer Ibrahim Qashush, nicknamed "the mocking bird of the revolution," was found dead in July 2011 with his throat slit and vocal chords ripped out.