It was active in rebel-held eastern Aleppo before the territory was seized by forces loyal to President Bashar al Assad.
Seven members of the White Helmets rescue group were shot dead Saturday by unidentified gunmen who stormed the volunteers' office in northwestern Syria, the group and opposition activists said.
"The attackers stole two ambulances, helmets and communication devices", Hossam Halaq told Anadolu Agency.More news: 2017-18 EPL season starts with seven-goal Arsenal-Leicester thriller
The organization stresses its neutrality and not supporting ay political or armed group - it receives funds from UK, Netherlands, Denmark, Germany, Japan and the US.
The observatory's director, Rami Abdel Rahman, said: "Colleagues came in the morning for the change of shift and found them dead".
White Helmets rescue workers carry victims of the auto bomb attack to receive medical treatment at Sarakeb city, Idlib, Syria, on April 15, 2017.More news: Liverpool boss Klopp makes worrying admission about Philippe Coutinho
The organization was nominated for the Noble Peace Prize in 2016 but didn't win - it commenced operations in 2013 and the volunteers have been known since 2014 as the White Helmets for the sake of the helmets they put on their heads.
Although its volunteers work in exclusively rebel-held areas, the group insists it is not partisan.
Critics have also claimed rebel fighters, including jihadists, operate in their ranks.More news: Alvaro Morata scores his first goal for Chelsea in defeat to Burnley
The attack occurred in the city of Sarmin in Idlib province, which is controlled by Hayat Tahrir Al-Sham, a coalition of Salafi jihadist groups that includes Fateh al-Sham.
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