State television also reported the attack, without mentioning the family ties between Ghazali, a Sunni Muslim, and the three men.
“An armed terrorist group attacked a number of people at a petrol station near the village of Qarfa, which led to the killing of one and the wounding of another,” Syria TV said, identifying the dead man as Hussam Ghazali.
It said the victim’s father Fayez was wounded, and Jalal Ghazali was abducted.
The Syrian Observatory for Human Rights gave the same report, but quoted local activists as saying the three men were relatives of Major General Rustom Ghazali.
It said rebels had attacked the Ghazali compound on the outskirts of Qarfa alongside the Deraa-Damascus highway.
According to the Syrian Revolution General Commission, Free Syrian Army rebels targeted a “gathering of security forces and shabiha (militiamen) in the Ghazali complex before noon.”
Rustom Ghazali’s nephew was killed, while his brother was wounded and another nephew was kidnapped, it said.
“The siblings of Major General Ghazali and their children were the worst shabiha for the people of the town of Qarfa and the province as a whole,” the activist network quoted residents as saying.
Deraa native Ghazali, 59, has been political security chief since his predecessor and three other senior security heads were killed in a Damascus bombing in July 2012.
Ghazali was the head of military intelligence in Lebanon from 2002 to 2005, when Syrian troops withdrew from its tiny neighbor after occupying it for three decades.
On the frontlines, fighting flared in areas around Damascus as opposition fighters seeking to topple President Bashar Assad try to push into the city itself. The opposition fighters advanced in the suburbs threaten the government’s grip on its seat of power, prompting a punishing response from the military on rebel areas skirting the capital.
Anti-regime activists circulated a video they said showed an explosion near a military intelligence office in the town of Nabk, north of the capital. They had no information on casualties and the government did not comment on the bombing.
Syria’s 21-month conflict has turned into a bloody stalemate that the United Nations says has killed more than 60,000 people, and it warns the civil war could claim the lives of many more this year. International efforts to stop the fighting have failed so far, and although rebels have made gains in recent months, they still can’t challenge Assad’s hold on much of the country.