"There have been 14,476 people killed since March 2011, among them 10,117 civilians, 3,552 soldiers and 807 army defectors," Rami Abdel Rahman, head of the Syrian Observatory for Human Rights, told AFP.
The civilian toll includes casualties among rebels who have taken up arms against the regime.
Since the implementation of a UN-Arab League brokered ceasefire on April 12, at least 3,353 people were killed, the majority of them in the past month.
"From May 13 to June 13, there were 2,302 people killed in Syria," Abdel Rahman said, listing 1,455 civilians, 96 dissidents and 751 soldiers, who accounted for nearly a third of the total.
"In the past month, there has been an escalation of clashes between regime forces and rebel troops as well as shelling, which has led to a sharp increase in casualties," the Observatory head said.
The rise in violence follows an assessment by UN peacekeeping chief Herve Ladsous on Tuesday that Syria was now locked in full-scale civil war, with regime forces having lost control of "large chunks of territory."