Those killed since March last year comprised 9 862 civilians, 3 470 soldiers and 783 army deserters, the Syrian Observatory for Human Rights said.
The Britain-based watchdog counts rebel fighters who are not deserters from the army as civilians.
The violence has intensified in Syria despite the presence of 300 United Nations observers charged with monitoring a truce that was supposed to take effect from April 12.
On Saturday, at least 111 people – 83 civilians and 28 soldiers – were killed, according to revised figures from the Observatory, representing one of the heaviest single-day death tolls since the nominal start of the ceasefire.
On Sunday, shelling of the town of Qusayr on the border with Lebanon killed an activist and five civilians, the Observatory said.
Three civilians were killed in a similar bombardment of the town of Talbisseh, 10km from the border, the Britain-based watchdog said.
Several districts of the central city of Homs also came under artillery and heavy machinegun fire by government forces, which left one person dead in the Khalidiyeh neighbourhood, the watchdog added.
Surveillance aircraft were seen flying over the city, where 12 civilians were killed on Saturday.
In the southern province of Daraa, at least two soldiers were killed in clashes with rebel fighters, which broke out at dawn near the village of Al-Sanmin, the watchdog said.
Hundreds of rebel fighters remained holed up in Latakia province, a loyalist stronghold on the Mediterranean coast.
The army sent troop reinforcements to the mainly Alawite province where rebels have grouped in a Sunni Muslim enclave around the town of Al-Heffa, the Observatory said.
Loyalist forces bombarded the town and surrounding villages for a sixth straight day, it said.
Nearly 60 soldiers have died since June 5 in battles with opposition fighters in the enclave, which lies some 50km from the Turkish border. At least 46 civilians and rebels have also been killed.
“The army is suffering its worst losses now in Al-Heffa, as hundreds of rebels are holed up in this area of steep mountains,” Observatory head Rami Abdel Rahman said.
He said that the resistance being put up in a province where the majority of the population are members of Assad’s Alawi minority showed that the uprising against his regime was truly nationwide.
“The coast is no longer a safe area, and the whole country is now involved in the revolt,” Abdel Rahman said.
In Idlib province, a rebel stronghold province in the northwest, thousands took part in a funeral procession in the town of Maaret al-Numan for nine of 13 civilians killed in shelling on Saturday, the Observatory said. – AFP