An electoral list backed by the Iran-backed Hezbollah lost a seat in its south Lebanon stronghold to a candidate backed by opposition groups in parliamentary polls on Sunday, an opposition candidate and two Hezbollah officials said, citing preliminary results.

Two Hezbollah officials said Elias Jradi, an eye doctor running on the opposition-backed "Together Towards Change" list, won an Orthodox Christian seat previously held by Assaad Hardan of the Syrian Socialist Nationalist Party, a close Hezbollah ally who has been an MP since 1992.

Jradi told Reuters his list had secured enough votes to win one seat, an opposition breakthrough in an area dominated by the Iran-backed group and its allies, but would not confirm it would go to him before results were finalised.

Shi'ite Muslim Hezbollah and its allies are expected to retain control of the remaining 10 seats in the district, the Hezbollah officials said.

The election for the 128-member parliament is the first since Lebanon collapsed into economic crisis in 2019. Results are expected to emerge through the night.

Hezbollah and its allies won a majority in 2018.