Rebel forces have killed nearly 80 Syrian soldiers in the past few days and activists claim the toll was more than 100.
The casualties represent some of the heaviest losses for government troops since the uprising began 15 months ago.
The Britain-based Syrian Observatory for Human Rights, which has a network of sources on the ground, said 113 soldiers have been killed in clashes with rebel forces across the country since Friday.
The figure was impossible to confirm independently, but the Syrian government confirmed nearly 80 soldiers had been killed over the past three days.
"The regime is suffering major losses," said Rami Abdul-Rahman, head of the Observatory.
Syria's uprising began with mostly peaceful protests, but a brutal government crackdown with tanks, machine guns and snipers led many in the opposition to take up arms. Now, the conflict has changed into an armed insurgency.
The violence has grown increasingly chaotic in recent months and it is difficult to assign blame for much of the bloodshed as the country spirals toward civil war.
The government restricts journalists from moving freely, making it nearly impossible to independently verify accounts from either side.
Videos and photographs posted online by activists showed destroyed tanks and armoured personnel carriers over the past few days. In a video posted online on Saturday, said to have been taken in the Damascus suburb of Douma, a personnel carrier is torn to pieces and at least two charred bodies of soldiers are seen near the vehicle.
Government spokesman Jihad Makdissi said last week that rebels are using sophisticated anti-tank missiles.
State-run news agency SANA said nearly 80 soldiers had been killed over the past three days. It said the dead include a brigadier general who was shot on his way to work in the restive northern province of Idlib.
Activists say more than 13,000 people have been killed since the crisis in Syria began in March last year.
The US State Department says international envoy to Syria Kofi Annan will be going to Washington on Friday to meet secretary of state Hillary Clinton.
Mr Annan is scheduled to brief an open meeting of the UN General Assembly on Syria on Thursday and then attend a closed Security Council meeting to discuss the latest developments. He has been pushing a six-point plan to ease Syria's crisis calling for stopping killings and launching an inclusive political process.
A ceasefire never took hold and the violence has continued despite the presence of UN observers in the country.