BEIRUT—Prominent Syrian-born Palestinian actor Mohammed Rafeh, who was believed to be a supporter of President Bashar Assad's regime, was kidnapped and then killed by anti-government gunmen, activists and his family said Sunday. He was 30.

Ahmad Rafeh, Mohammed's father and also a well-known actor, said the family received Mohammed's body Sunday.

"My son was killed in cold blood," Rafeh said by telephone from Damascus, adding that his son's body bore gunshot wounds to the head, neck and shoulder.

The Britain-based Syrian Observatory for Human Rights said Rafeh was kidnapped Friday night in the tense Damascus neighborhood of Barzeh, which has been hit by fighting between rebels and government troops. The Observatory said Rafeh was killed for apparently giving information to the regime about rebels and anti-government protesters.

Rafeh's killing comes days after a video posted online showing gunmen shooting dead captured soldiers—some of whom were wounded—raised concerns about rebel brutality at a time when the United States is making its strongest push yet to forge an opposition movement with which it can work.

U.N. officials and human rights groups believe President Bashar Assad's regime is responsible for the bulk of suspected war crimes in Syria's 19-month-old conflict, which began as a largely peaceful uprising but has shifted into a brutal civil war. But investigators of human rights abuses say rebel atrocities are on the

rise.

Activists say that more than 36,000 people have been killed since the uprising began in March last year.

Rafeh's death comes after a campaign began on social media calling for actors who support Assad to be punished.

A Facebook page titled "The black list of Syrian artists" carried a picture of Rafeh standing next to a wall with "Assad only" spray-painted on it.

"The reason was not difference of opinion. Mohammed Rafeh was a commander of a shabiha group," the caption read referring to pro-government gunmen who are known in Syria as shabiha.

The same page also posted a copy of a weapons license issued to Rafeh by the powerful Air Force Intelligence Agency. The license for a pistol had a Feb. 1, 2013 expiry date with his picture on it. The authenticity of the copy could not be verified.

It is not uncommon in Syria for actors to have a license for weapons from authorities to defend themselves in case they are in danger. It was not clear whether Rafeh had a pistol when he was kidnapped.

A video posted on YouTube by anti-government activists showed Rafeh on state TV saying that Syria "is protected by God, its people and the command."

The Popular Front for the Liberation of Palestine General Command, a Palestinian faction that strongly backs Assad, condemned the killing saying it was carried out by the "gangs of criminals in Syria."

Hussam Arafat, a member of the group's political bureau, said in a statement that Rafeh's murder "is a black mark of shame" of the killers.

Rafeh had played roles in several Syrian TV series but became famous throughout the Arab world five years ago for his role in the Bab al-Hara program that depicted life in Damascus in the 1930s under French colonial rule.

Rafeh played the role of Ibrahim, the son of a wealthy textile merchant, who fights against French forces in defense of Syria.

Rafeh was not married. The family said a funeral is planned for Monday.