BEIRUT, Lebanon — Activist groups said Sunday that about 5,000 people were killed in Syria's civil war in August, the highest figure reported in more than 17 months of fighting as President Bashar Assad's regime unleashed crushing air power against the revolt for the first time.
The U.N. children's fund UNICEF put the death toll for last week alone at 1,600, the largest weekly figure for the uprising.
Omar Idilbi, a Cairo-based activist with the Local Coordination Committees group, said, "The past month witnessed large massacres and the regime was conducting wide operations to try to crush the uprising. Last month's acts of violence were unprecedented."
He said the increased use of the air force and artillery bombardments was behind the spike in casualties.
The civil war witnessed a major turning point in August when Assad's forces began widely using air power to try to put down the revolt. The fighting also reached Syria's largest city, Aleppo, which had been relatively quiet for most of the uprising.
The Britain-based activist group Syrian Observatory for Human Rights said that 5,440 people, including 4,114 civilians, were killed in August. The LCC put the toll at 4,933 civilians.
On Sunday, the Observatory and the LCC said more than 100 people were killed throughout Syria. The groups have been reporting 100 to 250 deaths per day over the past week.
Syria's uprising has been the bloodiest in the Arab Spring that has already removed long-serving authoritarian leaders in Egypt, Tunisia, Yemen and Libya.
The two main activists groups also released new death tolls for the entire uprising since March 2011. The Observatory said more than 26,000 have been killed, including more than 18,500 civilians. The LCC put the death toll at more than 23,000 civilians. The LCC does not count members of the military who are killed, but the Observatory does.
The groups had previously reported a toll of around 20,000 more than a month ago.
As the death toll has mounted, international efforts to end the crisis have faltered badly. The United Nations and Arab League have both led prolonged but ultimately failed efforts to negotiate an end to the violence.