The Syrian army killed 62 rebel fighters in an apparent ambush at dawn on Wednesday. The incident happened near the town of Adra, which lies east of Damascus.
The deaths were reported by the Syrian Observatory for Human Rights, a monitoring group opposed to the country's current government.
While state news agency SANA acknowledged the attack, it did not give a death total for the rebels, reports Reuters. However, it did report that the rebels were part of the al-Nusra Front, a group linked to al Qaeda.
SANA added that all the rebels were killed by the Syrian army in the attack. The army then confiscated machine guns and rocket-propelled grenades.
While SANA said the "terrorists" (the government's term for the rebels) included non-Syrians, the Observatory said that eight of the rebels were still unaccounted for.
Assad's forces have been on the offensive against the rebels as the two sides continue a more than two-year-long civil war. More than 100,000 people have died since the conflict began in March 2011. Millions more have been displaced.
The BBC notes that the Observatory called the rebel fighters "martyrs," adding that they were mostly youths. The army remains in control of most of Damascus and routes in the west. Meanwhile, the rebels control areas in Syria's north and east.
The Syrian army ambush comes the day after rebels captured a key air base in Aleppo province near the Turkish border. The Menagh base is close to a key rebel supply route from Turkey.
But despite the gains made by rebels, forces loyal to Assad have done the same. Their gains have mostly been in Damascus, Homs, and some areas of Aleppo. The Syrian conflict has pushed the Middle East to the brink and revived sectarian tensions in countries like Iraq and Afghanistan.
It is unclear when, or if, the war will come to an end.