Hezbollah views events in Syria as a "major, dangerous and new transformation", a senior Hezbollah politician said on Monday, the Iran-backed group's first reaction to the toppling of its ally Bashar al-Assad.

Hezbollah played a major part propping up Assad through years of war in Syria, before bringing its fighters back to Lebanon over the last year to fight in a bruising war with Israel - a redeployment which weakened Syrian government lines.

His downfall has stripped Hezbollah of a vital ally along Lebanon's eastern border. Assad-ruled Syria long served as a vital conduit for Iran to supply weapons to the Shi'ite Islamist Hezbollah.

"What is happening in Syria is a major, dangerous and new transformation, and how and why what happened requires an evaluation, and the evaluation is not done on the podiums," Hezbollah lawmaker Hassan Fadlallah said in a statement.

Syrian armed groups led by the Sunni Islamist Hayat Tahrir al-Sham swept into Damascus on Sunday, seizing the capital and forcing Assad to leave for Russia.

Israel dealt heavy blows to Hezbollah during more than a year of hostilities, which began when the Lebanese group opened fire on Oct. 8, 2023 in solidarity with its Palestinian ally Hamas in Gaza. A ceasefire in Lebanon took effect on Nov. 27.