Deaths were reported in clashes and shelling on October 27 in Damascus Province, the northern city of Aleppo, Daraa in the south, and the eastern city of Deir Ezzor.
Among them were five killed in a car-bomb attack near a restaurant in Deir Ezzor, activists said.
State television blamed the attack on "terrorists" and said the bomb caused "significant damage" to the facade of a Christian church.
The AFP news agency reported that regime warplanes were seen flying over Aleppo and Damascus.
The head of the Syrian Observatory for Human Rights told the dpa news agency: "Neither side seems ready to stop. The truce looks set to collapse."
The London-based group reported that about 150 people were killed in bombings, artillery fire, and fighting on October 26 -- the first day of the cease-fire.
No End To Conflict
The international envoy on Syria, Lakhdar Brahimi, had earlier said the four-day truce could start the process of ending the 19-month conflict between Syrian government forces and rebels.
The Syrian Army and most rebel commanders said they would only observe the truce if the other side held their fire.
Previous attempts at cease-fires in Syria have collapsed.
The UN Security Council backed Brahimi's proposed cease-fire on October 24, but has been deadlocked over taking any stronger action to try and end the conflict.
China and Russia have vetoed resolutions calling for tougher action against President Bashar al-Assad.
The uprising against Assad's government started in March 2011.
Activists say more than 35,000 people have since been killed, while the United Nations estimates that at least 20,000 have died.