Air strikes have killed at least eight first responders from the Syria Civil Defence in Hama province, according to the group also known as The White Helmets.
Saturday's air strikes hit the rescuers' centre in Kafr Zita, located in northwestern Syria. Civilians who rushed to the scene to help were also struck, according to the Syria Civil Defence's Twitter posts.
The air strike was one of the deadliest against the rescuers who operate in opposition-held areas and who have grabbed world attention for operating in extreme conditions, pulling survivors out of recently struck areas.
The volunteers have often been targeted by government air strikes, in what are known as "double tap" attacks, as they work to rescue others.
The Syrian Civil Defence operates in much of Syria's rebel-controlled territory.
The group said five bodies were lifted from the rubble and the rescuers continue to look for the others
The Syrian Observatory for Human Rights (SOHR), a Britain-based monitoring group, said the number of those killed is likely to rise as the search mission continues.
It was not clear who carried out the air strikes, but Syrian government and Russian aircraft have targeted opposition-held areas.
Hama has been the scene of intense violence in recent weeks as the government attempts to push back a rebel offensive.
In an interview with Venezuela-based TeleSUR news network, President Bashar al-Assad blamed opposition groups for "destroying" the country's infrastructure and reiterated past claims that there were no "moderate" fighters among the opposition.
