BEIRUT – A Hezbollah commander and several fighters have been killed inside Syria, a Lebanese security official said Tuesday, a development that could stoke already soaring tensions over the Lebanese militant group's role in the civil war next door.

Hezbollah's reputation has taken a beating over its support for the Syrian regime, but any sign that the group's fighters are taking part in the battle raises fears that the conflict could expand into a wider fight engulfing the region.

Hezbollah has stood by Syrian President Bashar Assad since the uprising began 18 months ago, even after the group supported revolts in Egypt, Tunisia, Libya and Bahrain.