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 military deserters as civilians.
The violence has intensified despite the presence in Syria 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, in one of the heaviest single-day death tolls since the nominal start of the ceasefire.
By late on Sunday afternoon violence across Syria had killed at least 29 civilians, including 11 soldiers, the Observatory reported.
The troops were killed in clashes with armed rebels in the southern province of Daraa, in the central Homs province and in an attack on a military convoy in the eastern province of Deir Ezzor, it said.
Four civilians and an activist were killed in shelling of the town of Qusayr on the border with Lebanon, where rebels blew up a building housing government offices, the Observatory said.
Troops also shelled the Khalidiyeh neighbourhood of Homs city and other
neighbourhoods, killing three other civilians, as surveillance aircraft flew overhead, it added.
Another three civilians were killed in a similar bombardment of the town of Talbisseh, 10 kilometres (six miles) from the border, the Observatory said.
Another civilian was killed in the Homs province rebel town of Rastan, it added.
There was also bloodshed in the Deir al-Assafir region near Damascus, where a civilian was shot dead by security forces during search operations.
In the northwestern province of Idlib an elderly man was killed by regime forces while two other civilians died when helicopter gunships opened fire on the Hayyan region of the northern province of Aleppo, the NGO added.
Hundreds of rebels meanwhile 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 50 kilometres (30 miles) 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 told AFP.
He said the resistance in a province where most of the population are members of Assad’s Alawi minority showed that the uprising was truly nationwide.
“The coast is no longer a safe area, and the whole country is now involved in the revolt,” he said.
In Idlib province, a rebel stronghold province in the northwest, thousands joined a funeral procession in the town of Maaret al-Numan for nine of 13 civilians killed in shelling on Saturday, the Observatory said.
Source: BBC News