At least 15 Hezbollah fighters were killed on Saturday by Syrian rebels in the Ghouta district of Damascus, Al Arabiya television reported, citing opposition sources.
A video posted on the internet showed dead men with Hezbollah label patches on their uniforms. Six wounded Hezbollah fighters were reportedly transferred to Lebanon for medical treatment, according to Al Arabiya.
Hundreds of Hezbollah men have been reportedly killed in Syria since the start of the civil war there about two years ago.
Hezbollah has admitted sending soldiers to Syria, at first claiming it seeks to protect sacred Shiite religious sites against potential attacks by the Sunni rebels.
The group helped the Syrian regime’s army retake the town of Al-Qusayr, which borders Lebanon, in May 2013.
Hundreds were believed to be killed in the battle of Al-Qusayr, which began with heavy aerial bombardment. Rebels pulled out of the town after two weeks of fighting.
Iran, a major ally of Hezbollah and the Syrian regime, is also believed to have a strong military presence in Syria.
The intervention of Hezbollah in Syria has raised fears among some Lebanese that their country could become engulfed by its much larger neighbor's conflict.