A source close to Lebanon's Hezbollah said Saturday the group sent 2,000 fighters into Syria near the border, as its ally Damascus reels from a rebel offensive that has seized major cities in recent days.

"Hezbollah sent 2,000 fighters to the Qusayr area... to defend its positions there and has not yet participated in any battles" with Syrian rebels, the source told AFP, requesting anonymity to discuss sensitive matters.

The source said Hezbollah sent 150 military advisers to help government forces defend Homs if fighting erupts there.