A Syrian Arab Red Crescent volunteer was shot dead and three others were wounded in the town of Douma, on the outskirts of Damascus, the International Committee of the Red Cross (ICRC) said.
"We are saddened and extremely shocked by the death of Mohammed al-Khadraa," Dr Abdul Rahman al-Attar, the president of the Syrian Arab Red Crescent, said in a statement. "This is the third fatal incident involving the Red Crescent in less than eight months."
Khadraa was shot and killed on Tuesday in a vehicle clearly marked with the Red Crescent emblem, the statement said.
On Thursday, Syria's state news agency said an armed terrorist group killed Khadraa when it opened fire on a Red Crescent ambulance, but did not give details on the group.
Opposition activists, who have been trying for over a year to topple President Bashar al-Assad, said that government forces have been shelling Douma with mortar bombs for a week.